Use these links to rapidly review the document
Table of Contents
TABLE OF CONTENTS

Table of Contents

The information contained in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. A registration statement relating to the securities has been declared effective by the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED JULY 28, 2014

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-175822

P R E L I M I N A R Y    P R O S P E C T U S    S U P P L E M E N T
(To prospectus dated August 18, 2011)

8,000,000 Shares

Common Stock

---

        We are offering 8,000,000 shares of our common stock.

        Our common stock is listed on the New York Stock Exchange under the symbol "HIL." On July 25, 2014, the last sale price of the shares as reported on the New York Stock Exchange was $5.78 per share.

        Investing in our common stock involves risks. See "Risk Factors" beginning on page S-15 of this prospectus supplement.

---

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

        The underwriters may also purchase up to 1,200,000 additional shares of common stock from us, at the public offering price, less the underwriting discount, within 30 days from the date of this prospectus supplement.

        Delivery of the shares of common stock is expected to be made on or about                , 2014.

---

KeyBanc Capital Markets

Boenning & Scattergood, Inc.           Sidoti & Company, LLC           SOCIETE GENERALE

---

   

The date of this prospectus supplement is                    , 2014.

---

Table of Contents

TABLE OF CONTENTS

---

S-i

---

Table of Contents

ABOUT THIS PROSPECTUS SUPPLEMENT

        This document consists of two parts. The first part is the prospectus supplement, which describes the specific terms of the offering. The second part is the prospectus, which describes more general information, some of which may not apply to the offering. You should read both this prospectus supplement and the accompanying prospectus, together with additional information described under the headings "Where You Can Find More Information" and "Incorporation of Certain Documents by Reference" in this prospectus supplement and the accompanying prospectus.

        All references in this prospectus supplement to "Hill," the "Company," "we," "us," "our," the "registrant" or similar references mean Hill International, Inc. and include our consolidated subsidiaries where the context so requires. When we refer to the "common stock" we refer to shares of our common stock, par value $0.0001 per share.

        If the information set forth in this prospectus supplement differs in any way from the information set forth in the accompanying prospectus, you should rely on the information set forth in this prospectus supplement.

        You should rely only on the information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus or in any free writing prospectus that we have authorized for use in connection with this offering. We have not, and the underwriters have not, authorized anyone to provide you with information different than that contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus or in any free writing prospectus that we have authorized for use in connection with this offering. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give. If anyone provides you with different or inconsistent information, you should not rely on it. You should not assume that the information contained in this prospectus supplement, the accompanying prospectus, any document incorporated by reference or any free writing prospectus is accurate as of any date, other than the date mentioned on the cover page of these documents. Our business, financial condition, results of operations and prospects may have changed since such date.

        We are not, and the underwriters are not, making an offer to sell the securities described in this prospectus supplement in any jurisdiction in which an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation. Neither this prospectus supplement nor the accompanying prospectus constitutes an offer, or an invitation on our behalf or on behalf of the underwriters or any agents, to subscribe for and purchase any of the securities and may not be used for or in connection with an offer or solicitation by anyone, in any jurisdiction in which such an offer or solicitation is not authorized or to any person to whom it is unlawful to make such an offer or solicitation.

S-ii

---

Table of Contents

 

S-1

---

Table of Contents

S-2

---

Table of Contents

S-3

---

Table of Contents

S-4

---

Table of Contents

S-5

---

Table of Contents

S-6

---

Table of Contents

 

S-7

---

Table of Contents

S-8

---

Table of Contents

S-9

---

Table of Contents

S-10

---

Table of Contents

S-11

---

S-12

---

Table of Contents

S-13

---

S-14

---

Table of Contents

RISK FACTORS

        The following risks and uncertainties pertain to this offering, our common stock and the Refinancing. Other risks that we face, are more fully described under the section entitled "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended December 31, 2013, as filed with the SEC on March 14, 2014 and incorporated by reference in this prospectus supplement (see the section entitled "Incorporation of Certain Documents by Reference" in this prospectus supplement), including risks related to the collectibility of our accounts receivable from our contracts in Libya.

Risks Related to this Offering and Ownership of Our Common Stock

The market price for our common stock could be volatile and could decline, resulting in a substantial or complete loss of your investment.

        The stock markets, including the New York Stock Exchange on which our common stock is listed, have experienced significant price and volume fluctuations. As a result, the market price of our common stock could be similarly volatile, and investors in our common stock may experience a decrease in the value of their shares, including decreases unrelated to our operating performance or prospects. The price of our common stock could be subject to wide fluctuations in response to a number of factors, including:

•

our operating performance and the performance of other similar companies;



•

actual or anticipated differences in our operating results;



•

changes in our revenue or earnings estimates or recommendations by securities analysts;



•

publication of research reports about us or our industry by securities analysts;



•

additions and departures of key personnel;



•

speculation in the press or investment community;



•

actions by institutional stockholders;



•

changes in accounting principles;



•

terrorist acts and other events affecting political, economic or civil conditions in one or more foreign countries in which we operate; and



•

general economic and market conditions, including factors unrelated to our performance.

Future sales of our common and preferred stock may depress the price of our common stock.

        As of June 30, 2014, there were 40,742,349 shares of our common stock outstanding and an additional 7,518,620 shares of our common stock may be issued upon the exercise of options held by employees, management and directors. We also have the authority to issue up to 1,000,000 shares of preferred stock upon terms that are determined by our Board of Directors and, as of June 30, 2014, additional options to purchase up to 1,941,974 shares of our common stock without stockholder approval. In addition, in 2011, we registered with the SEC the potential issuance of 20,000,000 shares of common stock on a registration statement on Form S-3 (which amount includes the shares of common stock that may be issued and sold pursuant to this offering) and 8,000,000 shares of common stock on a registration statement on Form S-4 (of which 6,438,923 shares of common stock remain available for issuance). These shares may be used for working capital and general corporate purposes, or used in future acquisitions, respectively, subject to the covenants of any existing and future outstanding indebtedness. Sales of a substantial number of these shares in the public market, or factors relating to the terms we may determine for our preferred stock, options or warrants, could decrease the market price of our common stock. In addition, the perception that such sales might occur may cause

S-15

---

Table of Contents

the market price of our common stock to decline. Future issuances or sales of our common stock could have an adverse effect on the market price of our common stock.

Because we have no current plans to pay cash dividends on our common stock, you may not receive any return on investment unless you sell your common stock for a price greater than that which you paid for it.

        We may retain future earnings, if any, for future operations, acquisitions and debt repayment and have no current plans to pay any cash dividends. Any decision to declare and pay dividends in the future will be made at the discretion of our Board of Directors and will depend on, among other things, our results of operations, financial condition, cash requirements, contractual restrictions and other factors that our Board of Directors may deem relevant. In addition, our ability to pay dividends may be limited by covenants of any existing and future outstanding indebtedness we or our subsidiaries incur, including the agreements governing our Existing Credit Agreement, Existing Term Loan and the new Secured Credit Facilities. As a result, you may not receive any return on an investment in our common stock unless you sell our common stock for a price greater than that which you paid for it.

We are able to issue shares of preferred stock with greater rights than our common stock.

        Our Board of Directors is authorized to issue one or more series of preferred stock from time to time without any action on the part of our stockholders. Our Board of Directors also has the power, without stockholder approval, to set the terms of any such series of preferred stock that may be issued, including voting rights, dividend rights and preferences over our common stock with respect to dividends and other terms. If we issue preferred stock in the future that has a preference over our common stock with respect to the payment of dividends or other terms, or if we issue preferred stock with voting rights that dilute the voting power of our common stock, the rights of holders of our common stock or the market price of our common stock could be adversely affected.

Provisions in our organizational documents and Delaware law could discourage potential acquisition proposals, could delay or prevent a change in control of the Company that our stockholders may consider favorable and could adversely affect the market value of our common stock.

        Provisions in our organizational documents and Delaware law could discourage potential acquisition proposals, could delay or prevent a change in control of the Company that our stockholders may consider favorable and could adversely affect the market value of our common stock. Our amended and restated certificate of incorporation and amended and restated bylaws include provisions that:

•

our Board of Directors is expressly authorized to make, alter or repeal our bylaws;



•

our Board of Directors is divided into three classes of service with staggered three-year terms. This means that only one class of directors will be elected at each annual meeting of stockholders, with the other classes continuing for the remainder of their respective terms;



•

our Board of Directors is authorized to issue preferred stock without stockholder approval;



•

only our Board of Directors, our Chairman of the Board, our Chief Executive Officer or the holders of a majority in amount of our capital stock issued and outstanding and entitled to vote may call a special meeting of stockholders; this means that minority stockholders cannot force stockholder consideration of a proposal, including a proposal to replace our Board of Directors, by calling a special meeting of stockholders prior to such time authorized by our Board of Directors, our Chairman of the Board, our Chief Executive Officer or the holders of a majority in amount of our capital stock issued and outstanding and entitled to vote;



•

our bylaws require advance notice for stockholder proposals and director nominations;

S-16

---

Table of Contents

•

our bylaws limit the removal of directors and the filling of director vacancies; and



•

we will indemnify officers and directors against losses that may incur in connection with investigations and legal proceedings resulting from their services to us, which may include services in connection with takeover defense measures.

These provisions may make it more difficult for stockholders to take specific corporate actions and could have the effect of delaying or preventing a change in control of the Company.

        In addition, Section 203 of the General Corporation Law of the State of Delaware imposes certain restrictions on mergers and other business combinations between the Company and any holder of 15% or more of our outstanding common stock. This provision is applicable to Hill and may have an anti-takeover effect that may delay, defer or prevent a tender offer or takeover attempt that a stockholder might consider in the stockholder's best interest. In general, Section 203 could delay for three years and impose conditions upon "business combinations" between an "interested shareholder" and Hill, unless prior approval by our Board of Directors is given. The term "business combination" is defined broadly to include mergers, asset sales and other transactions resulting in financial benefit to a stockholder. An "interested shareholder," in general, would be a person who, together with affiliates and associates, owns, or within three years did own, 15% or more of a corporation's voting stock.

A small number of shareholders own a large number of shares thereby potentially exerting significant influence over us.

        As of June 30, 2014, Irvin E. Richter, David L. Richter and other members of the Richter family beneficially owned approximately 32% of our common stock. This concentration of ownership could significantly influence matters requiring stockholder approval and could delay, deter or prevent a change in control of the Company or other business combinations that might otherwise be beneficial to our other stockholders. Accordingly, this concentration of ownership may impact the market price of our common stock. In addition, the interest of our significant stockholders may not always coincide with the interest of the Company's other stockholders. In deciding how to vote on such matters, they may be influenced by interests that conflict with our other stockholders.

Risks Related to the Refinancing

We may not be able to consummate the contemplated Refinancing, which could negatively impact our interest expense. Our inability to consummate the Refinancing could also materially and adversely affect our liquidity and our ongoing results of operation.

        Our Existing Credit Agreement and Existing Term Loan mature on March 31, 2015 and October 18, 2016, respectively. If we are not able to consummate the contemplated Refinancing, we may not be able to renew or otherwise refinance either or both of our Existing Credit Agreement and Existing Term Loan, or any renewal or refinancing may occur on less favorable terms. If we are unable to refinance or renew our Existing Credit Agreement and Existing Term Loan, our failure to repay all amounts due on the applicable maturity date would cause a default under the terms of the Existing Credit Agreement and Existing Term Loan. In addition, our interest expense may increase significantly if we refinance or renew our Existing Credit Agreement or Existing Term Loan on terms that are less favorable to us than the current terms.

S-17

---

Table of Contents

DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

        Certain of the statements contained in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference in this prospectus supplement are considered "forward-looking statements" within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. The Private Securities Litigation Reform Act of 1995 provides certain "safe harbor" provisions for forward-looking statements. All forward-looking statements made in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference in this prospectus supplement are made pursuant to the Private Securities Litigation Reform Act. Except for historical information contained in this prospectus supplement, the matters set forth herein are forward-looking statements. These forward-looking statements provide current expectations of future events based on certain assumptions and include any statement that does not directly relate to any historical or current fact. Although we believe that the expectations, estimates and assumptions reflected in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in any of our forward-looking statements. You can identify forward-looking statements by the use of terminology such as "may," "will," "anticipate," "believe," "estimate," "expect," "future," "intend," "plan," "could," "should," "potential" or "continue" or the negative or other variations thereof, as well as other statements regarding matters that are not historical fact.

        Those forward-looking statements may concern, among other things:

•

the markets for our services;



•

projections of revenues and earnings, anticipated contractual obligations, capital expenditures, funding requirements or other financial items;



•

statements concerning our plans, strategies and objectives for future operations; and



•

statements regarding future economic conditions or performance.

        Important factors that could cause our actual results, performance or achievements to differ materially from estimates or projections contained in our forward-looking statements include:

•

modifications and termination of client contracts;



•

control and operational issues pertaining to business activities that we conduct pursuant to joint ventures with other parties;



•

difficulties we may incur in implementing our acquisition strategy;



•

the need to retain and recruit key technical and management personnel; and



•

unexpected adjustments and cancellations related to our backlog.

        Other factors that may affect our businesses, financial position or results of operations include:

•

our ability to consummate the new debt facilities;



•

the risk that our proposed lender will not be able to consummate the new debt facilities;



•

our ability to consummate the equity offering,



•

special risks regarding our ability to obtain debt financing or otherwise raise capital to meet required working capital needs and to support potential future acquisition activities;



•

special risks of international operations, including uncertain political and economic environments, acts of terrorism or war, potential incompatibilities with foreign joint venture partners, foreign currency fluctuations, civil disturbances and labor issues; and

S-18

---

Table of Contents

•

special risks of contracts with governmental entities, including the failure of applicable governing authorities to take necessary actions to secure or maintain funding for particular projects with us, the unilateral termination of contracts by the government and reimbursement obligations to the government for funds previously received.

        Other factors that could cause our actual results, performance or achievements to differ materially from that contemplated by forward-looking statements are discussed under the heading "Risk Factors" in this prospectus supplement, under the heading "Risk Factors" and in other sections of our Annual Report on Form 10-K for the year ended December 31, 2013, as well as in our other reports filed from time to time with the SEC that are incorporated by reference into this prospectus supplement.

        Because the risk factors referred to above could cause actual results or outcomes to differ materially from those expressed in any forward-looking statements made by us or on our behalf, you should not place undue reliance on any forward-looking statements. Except to the extent required by applicable laws and regulations, we undertake no obligation to update these forward-looking statements to reflect events or circumstances after the date of this prospectus supplement or to reflect the occurrence of unanticipated events. All subsequent written and oral forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the cautionary statements contained throughout this prospectus or in any prospectus supplement or in the information incorporated by reference herein or therein.

S-19

---

Table of Contents

USE OF PROCEEDS

        We estimate that our net proceeds from the sale of 8,000,000 shares of common stock in this offering will be approximately $            , or approximately $            if the underwriters exercise their option to purchase additional shares in full, after deducting underwriting discounts and commissions and our estimated offering expenses of $            .

        As required under the Commitment Letter, we intend to keep $10.0 million of the net proceeds of this offering as cash or cash equivalents until the closing of the Secured Credit Facilities and use the balance of the net proceeds to repay outstanding borrowings under our Existing Credit Agreement and Existing Term Loan, which amounted to $42.6 million and $88.7 million, respectively, at June 30, 2014. The payoff amount of the Existing Term Loan will be the loan's par value of $100.0 million. Upon the closing of the Secured Credit Facilities, we intend to use the $10.0 million of the net proceeds of this offering referenced above for general working capital purposes. At June 30, 2014, the weighted average interest rate on the outstanding borrowings under our Existing Credit Agreement and Term Loan were approximately 7.22% and 20.00% per annum, respectively. Our Existing Credit Agreement matures on March 31, 2015 and our Existing Term Loan matures on October 18, 2016.

        In addition to providing short-term borrowings used for working capital, the Company used borrowings under the Existing Credit Agreement and Existing Term Loan during the preceding 12 months to supplement funding from other sources for our general corporate purposes, which included, but was not limited to, operating costs, additional equity interests, payment of second installment note in connection with an acquisition and capital expenditures.

S-20

---

Table of Contents

CAPITALIZATION

        The following table sets forth our cash and cash equivalents and our capitalization as of March 31, 2014:

•

on an actual basis; and



•

on an as adjusted basis to give effect to the sale by us of 8,000,000 shares of our common stock in this offering, after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us, and the application of the estimated net proceeds of $             million from this offering (refer to "Use of Proceeds").

        This table should be read with "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our financial statements and notes thereto incorporated by reference in this prospectus supplement.

S-21

---

Table of Contents

UNDERWRITING

        Subject to the terms and conditions set forth in an underwriting agreement by and between KeyBanc Capital Markets Inc., as representative for the underwriters named in the agreement, and us, we have agreed to sell to each underwriter, and each underwriter has severally agreed to purchase from us, the number of shares of common stock set forth opposite its name in the table below:

        Under the terms of the underwriting agreement, the underwriters are committed to purchase all of these shares if any shares are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

        We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make because of any of those liabilities.

        The underwriting agreement provides that the underwriters' obligations to purchase the common stock depends on the satisfaction of the conditions contained in the underwriting agreement. The conditions contained in the underwriting agreement include the requirement that the representations and warranties made by us to the underwriters are true, that there is no material change in the financial markets and that we deliver to the underwriters customary closing documents.

        The underwriters propose to offer the shares of common stock directly to the public at the public offering price set forth on the cover of this prospectus and to certain dealers at such price less a concession not in excess of $    per share. If all of the shares are not sold at the public offering price, the representative of the underwriters may change the public offering price and the other selling terms.

        We have granted the underwriters an option to purchase up to 1,200,000 additional shares from us at the public offering price less the underwriting discount. The underwriters may exercise the option for 30 days from the date of this prospectus. If the underwriters exercise this option, each will be obligated, subject to conditions contained in the underwriting agreement, to purchase a number of additional shares of common stock proportionate to that underwriter's initial amount reflected in the above table.

        The following table shows the per share and total underwriting discount that we will pay to the underwriters. These amounts are shown assuming both no exercise and full exercise of the underwriters' option to purchase additional shares.

S-22

---

Table of Contents

        We estimate that the total expenses related to this offering payable by us, excluding underwriting discounts and commissions, will be approximately $            .

        We, our executive officers and directors and certain affiliates thereof have agreed with the underwriters, for a period of 90 days after the date of this prospectus, subject to certain exceptions, not to offer, sell, hedge or otherwise dispose of any shares of common stock or any securities convertible into or exchangeable for shares of our common stock, without the prior written consent of KeyBanc Capital Markets Inc. Immediately after this offering, 11,353,801 shares of common stock will be beneficially owned by our executive officers and directors and certain affiliates thereof. However, KeyBanc Capital Markets Inc. may, in its sole discretion and at any time without notice, release all or any portion of the securities subject to these lock-up agreements. When determining whether to release securities from the lock-up agreements, KeyBanc Capital Markets Inc. may consider, among other factors, market conditions at the time, the number of securities for which the release is requested and the stockholder's reasons for requesting the release. Notwithstanding the foregoing, if, under certain circumstances during the term of this lock-up, we issue an earnings release or announce that we will release earnings or material news or a material event regarding our company occurs, then the lock-up period will continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.

        Until the distribution of the shares of our common stock is completed, SEC rules may limit the underwriters from bidding for and purchasing our common stock. However, the underwriters may engage in transactions that stabilize the price of our common stock, such as bids or purchases of shares in the open market while this offering is in progress to peg, fix, or maintain that price. These transactions also may include short sales and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of shares than they are required to purchase in this offering. "Covered" short sales are sales made in an amount not greater than the underwriters' option to purchase additional shares from us. The underwriters may reduce that short position by purchasing shares in the open market or by exercising all or part of the option to purchase additional shares described above. In determining the source of shares to close out the covered short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase additional shares pursuant to the option granted to them. "Naked" short sales are any sales in excess of such option. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market after pricing that could adversely affect investors who purchase in this offering.

        The underwriters may also impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representative has repurchased shares of our common stock sold by or for the account of such underwriter in stabilizing or short covering transactions.

        Neither we nor the underwriters make any representation or prediction as to the effect the transactions described above may have on the price of our common stock. Any of these activities may have the effect of preventing or retarding a decline in the market price of our common stock. They may also cause the price of our common stock to be higher than the price that would otherwise exist on the open market in the absence of these transactions. The underwriters may conduct these transactions on the NYSE or in the over-the-counter market, or otherwise. If the underwriters commence any of these transactions, they may discontinue them without notice at any time.

        In connection with the offering, certain of the underwriters or securities dealers may distribute prospectuses by electronic means, such as e-mail.

S-23

---

Table of Contents

        Certain of the underwriters and their respective affiliates have engaged in, and may in the future engage in, investment banking and other transactions with us and perform services for us in the ordinary course of their business. They have received customary fees and commissions for those transactions. In the course of their businesses, the underwriters and their respective affiliates may actively trade our securities or loans for their own account or for the accounts of customers, and, accordingly, the underwriters and their respective affiliates may at any time hold long or short positions in such securities or loans.

        SG Americas Securities, LLC is acting as the sole and exclusive bookrunner and sole and exclusive arranger for the Secured Credit Facilities and one of its affiliates will act as the sole administrative agent and collateral agent for, and as a lender under, the Secured Credit Facilities. Houlihan Lokey Capital, Inc. will receive an advisory fee in connection with our entry into the Secured Credit Facilities.

S-24

---

Table of Contents

LEGAL MATTERS

        The validity of the shares of common stock offered by this prospectus supplement will be passed upon for us by Duane Morris LLP, Philadelphia, Pennsylvania. Certain legal matters will be passed upon for the underwriters by Jones Day, Cleveland, Ohio.

EXPERTS

        The consolidated financial statements of Hill International, Inc. at December 31, 2013 and for each of the years in the three-year period ended December 31, 2013, the related financial statement schedule, and management's assessment of the effectiveness of internal control over financial reporting as of December 31, 2013 have been audited by EisnerAmper LLP, independent registered public accounting firm, as set forth in their reports incorporated by reference herein, and are included in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any materials we file with the SEC at the following location of the SEC:

Public Reference Room
100 F Street, NE
Washington, DC 20549

        You may obtain information about the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC also maintains a website that contains reports, proxy and information statements and other information that we electronically file with the SEC, which you can access over the Internet at www.sec.gov. You can also obtain information about us at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

        The SEC allows us to "incorporate by reference" into this prospectus supplement and the accompanying prospectus the information we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any information referenced this way is considered to be part of this prospectus supplement and the accompanying prospectus, and any information that we file later with the SEC will automatically update and, where applicable, supersede this information. We incorporate by reference the following documents that we have filed with the SEC (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with the SEC's rules):

        (a)   Our Annual Report on Form 10-K for the year ended December 31, 2013, as filed with the SEC on March 14, 2014;

        (b)   Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2014, as filed with the SEC on May 12, 2014; and

        (c)   Our Current Reports on Form 8-K filed with the SEC on January 31, 2014, June 13, 2014 and July 28, 2014.

        For purposes of the registration statement of which this prospectus is a part, any statement contained in a document incorporated or deemed to be incorporated herein by reference shall be deemed to be modified or superseded to the extent that a statement contained herein modifies or supersedes such statement in such document. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of the registration statement of which this prospectus is a part.

S-25

---

Table of Contents

        We also incorporate by reference any future filings we make with the SEC (other than information furnished pursuant to Item 2.02 or Item 7.01 of Form 8-K or as otherwise permitted by the SEC's rules) under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, until we have sold all of the shares of common stock to which this prospectus supplement relates or the offering is otherwise terminated.

        This prospectus supplement and the accompanying prospectus is part of a registration statement on Form S-3 we have filed with the SEC relating to the shares of common stock. As permitted by SEC rules, this prospectus supplement and the accompanying prospectus do not contain all of the information included in the registration statement and the accompanying exhibits and schedules we file with the SEC. We have filed or incorporated by reference certain legal documents that control the terms of the shares of common stock offered by this prospectus supplement as exhibits to the registration statement. We may file certain other legal documents that control the terms of the shares of common stock offered by this prospectus supplement as exhibits to reports we file with the SEC. You may refer to the registration statement and the exhibits and schedules for more information about us and our common stock. The registration statement and exhibits and schedules are also available at the SEC's Public Reference Room or through its website.

        You may obtain a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

William H. Dengler, Jr.
Senior Vice President, General Counsel and Secretary
Hill International, Inc.
303 Lippincott Centre
Marlton, NJ 08053
Telephone: (856) 810-6200

        Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference.

S-26

---

Table of Contents

PROSPECTUS

20,000,000 Shares

HILL INTERNATIONAL, INC.

Common Stock

        From time to time in one or more offerings we may offer and sell up to 20,000,000 shares of common stock at prices and on terms described in one or more supplements to this prospectus, to be determined at or prior to the time of sale.

        This prospectus describes some of the general terms that may apply to an offering of shares of our common stock and the general manner in which they may be offered. The specific terms and any other information relating to a specific offering including the specific manner in which the securities may be offered, will be set forth in a supplement to this prospectus. The prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and each applicable prospectus supplement carefully before you invest, as well as the documents incorporated by reference in this prospectus and the applicable prospectus supplement.

        Our common stock is listed for trading on the New York Stock Exchange under the trading symbol "HIL." On July 22, 2011, the last reported sale price of our common stock on the New York Stock Exchange was $6.05 per share.

        We may offer and sell shares of common stock to or through one or more underwriters, dealers and agents, or directly to purchasers, on a continuous or delayed basis. See "Plan of Distribution." Each prospectus supplement will provide the amount, price and terms of the plan of distribution relating to the shares of common stock to be sold pursuant to such prospectus supplement. We will set forth the names of any underwriters, dealers or agents in the accompanying prospectus supplement, as well as the net proceeds we expect to receive from such sale.

        Investing in shares of our common stock involves risks. You should review carefully the risks and uncertainties described under the heading "Risk Factors" contained in the applicable prospectus supplement we have authorized for use in connection with a specific offering, and under similar headings in the documents that are incorporated by reference into this prospectus.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

   

The date of this prospectus is August 18, 2011.

---

Table of Contents

TABLE OF CONTENTS

2

---

Table of Contents

ABOUT THIS PROSPECTUS

        This prospectus is part of a registration statement that we filed with the United States Securities and Exchange Commission, or the SEC, using a "shelf" registration process. Under this shelf registration process, we may, from time to time, offer and sell up to 20,000,000 shares of our common stock in one or more offerings.

        This prospectus provides you with a general description of the shares of common stock offered by us. Each time we sell shares of common stock, we will provide a prospectus supplement, information that is incorporated by reference into this prospectus, or other offering material that will contain specific information about the terms of that offering. The prospectus supplement and any other offering material may also add to, update or change information contained in the prospectus or in documents we have incorporated by reference into this prospectus and, accordingly, to the extent inconsistent, information in or incorporated by reference in this prospectus is superseded by the information in the prospectus supplement and any other offering material related to such common stock.

        The prospectus supplement to be attached to the front of this prospectus may describe, as applicable:

•

The number of shares of common stock that we propose to sell;



•

The public offering price per share of the common stock;



•

The names of any underwriters, agents or dealers through or to which the shares of the common stock will be sold;



•

Any compensation to those underwriters, agents or dealers;



•

Any additional risk factors applicable to the shares of our common stock or our business and operations; and



•

Any other material information about the offering and sale of the shares of common stock.

        You should read carefully the entire prospectus, as well as the documents incorporated by reference in the prospectus, the applicable prospectus supplement and any other offering material, before making an investment decision.

        In this prospectus, references to "Company," "we," "us," "our," "registrant" and "Hill" refer to Hill International, Inc., a corporation organized under the laws of the State of Delaware, and its consolidated subsidiaries.

        You should rely only on the information contained or incorporated by reference in this prospectus, any prospectus supplement and any other offering material. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not making an offer to sell these securities in any jurisdiction where the offer and sale is not permitted. You should not assume that the information appearing in this prospectus, any prospectus supplement, any other offering material or the documents incorporated by reference herein or therein is accurate as of any date other than their respective dates, regardless of the time of delivery of this prospectus, any prospectus supplement, any other offering material or any sale of shares of common stock. Our business, financial condition, results of operations and prospects may have changed since those dates.

3

---

Table of Contents

WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any materials we file with the SEC at the following location of the SEC:

Public Reference Room
100 F Street, N.E., Room 1580
Washington, D.C. 20549

        You may obtain information about the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC also maintains a website that contains reports, proxy and information statements and other information that we electronically file with the SEC, which you can access over the Internet at www.sec.gov. You can also obtain information about us at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

        The SEC allows us to "incorporate by reference" into this prospectus the information we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any information referenced this way is considered to be part of this prospectus, and any information that we file later with the SEC will automatically update and, where applicable, supersede this information. We incorporate by reference the following documents that we have filed with the SEC (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with the SEC's rules):

(a)

Our Annual Report on Form 10-K for the year ended December 31, 2010;



(b)

Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2011;



(c)

Our Current Report on Form 8-K filed on June 8, 2011; and



(d)

Our Current Report on Form 8-K filed on July 7, 2011.

        We also incorporate by reference any future filings we make with the SEC (other than information furnished pursuant to Item 2.02 or Item 7.01 of Form 8-K or as otherwise permitted by the SEC's rules) under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), until we have sold all of the shares of common stock to which this prospectus relates or the offering is otherwise terminated.

        This prospectus is part of a registration statement on Form S-3 we have filed with the SEC relating to the shares of common stock. As permitted by SEC rules, this prospectus does not contain all of the information included in the registration statement and the accompanying exhibits and schedules we file with the SEC. We have filed or incorporated by reference certain legal documents that control the terms of the shares of common stock offered by this prospectus as exhibits to the registration statement. We may file certain other legal documents that control the terms of the shares of common stock offered by this prospectus as exhibits to reports we file with the SEC. You may refer to the registration statement and the exhibits and schedules for more information about us and our common stock. The registration statement and exhibits and schedules are also available at the SEC's Public Reference Room or through its website.

4

---

Table of Contents

        You may obtain a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

William H. Dengler, Jr.
Senior Vice President, General Counsel and Secretary
Hill International, Inc.
303 Lippincott Centre
Marlton, NJ 08053
Telephone: (856) 810-6200

        Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference.

DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

        Some of the statements contained in this prospectus, any prospectus supplement, any other offering material and any documents we incorporate by reference in this prospectus are considered "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Exchange Act. The Private Securities Litigation Reform Act of 1995 provides certain "safe harbor" provisions for forward-looking statements. All forward-looking statements made in this prospectus, any prospectus supplement, any other offering material and any documents we incorporate by reference are made pursuant to the Private Securities Litigation Reform Act. Except for historical information contained in this prospectus, the matters set forth herein are forward-looking statements. These forward-looking statements are based on our current expectations, estimates and assumptions and are subject to certain risks and uncertainties. Although we believe that the expectations, estimates and assumptions reflected in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in any of our forward-looking statements. You can identify forward-looking statements by the use of terminology such as "may," "will," "anticipate," "believe," "estimate," "expect," "future," "intend," "plan," "could," "should," "potential" or "continue" or the negative or other variations thereof, as well as other statements regarding matters that are not historical fact.

        Those forward-looking statements may concern, among other things:

•

The markets for our services;



•

Projections of revenues and earnings, anticipated contractual obligations, capital expenditures, funding requirements, possible transactional synergies or other benefits or other financial items;



•

Statements concerning our plans, strategies and objectives for future operations or our ability to consummate particular transactions; and



•

Statements regarding future economic conditions or performance.

        Important factors that could cause our actual results, performance and achievements, or industry results to differ materially from estimates or projections contained in our forward-looking statements include:

•

Modifications and termination of client contracts;



•

Control and operational issues pertaining to business activities that we conduct pursuant to joint ventures with other parties;



•

Difficulties we may incur in implementing our acquisition strategy and specific issues we encounter as we seek to consummate particular acquisitions;



•

The need or ability to retain and recruit key technical and management personnel; and

5

---

Table of Contents

•

Unexpected adjustments and cancellations related to our backlog or other measures, including those relating to acquisitions and potential acquisitions.

        Other factors that may affect our businesses, financial position or results of operations include:

•

Special risks of international operations, including uncertain political and economic environments, acts of terrorism or war, potential incompatibilities with foreign joint venture partners, foreign currency fluctuations, civil disturbances and labor issues; and



•

Special risks of contracts with governmental entities, including the failure of applicable governing authorities to take necessary actions to secure or maintain funding for particular projects with us, the unilateral termination of contracts by the government and reimbursement obligations to the government for funds previously received.

        Other factors that could cause our actual results, performance or achievements to differ materially from that contemplated by forward-looking statements are discussed under the heading "Risk Factors" and in other sections of our Annual Report on Form 10-K for the year ended December 31, 2010, as well as in our other reports filed from time to time with the SEC that are incorporated by reference into this prospectus and in the applicable prospectus supplement.

BECAUSE THE RISK FACTORS REFERRED TO ABOVE COULD CAUSE ACTUAL RESULTS OR OUTCOMES TO DIFFER MATERIALLY FROM THOSE EXPRESSED IN ANY FORWARD-LOOKING STATEMENTS MADE BY US OR ON OUR BEHALF, YOU SHOULD NOT PLACE UNDUE RELIANCE ON ANY FORWARD-LOOKING STATEMENTS. EXCEPT TO THE EXTENT REQUIRED BY APPLICABLE LAWS AND REGULATIONS, HILL UNDERTAKES NO OBLIGATIONS TO UPDATE THESE FORWARD-LOOKING STATEMENTS TO REFLECT EVENTS OR CIRCUMSTANCES AFTER THE DATE OF THIS PROSPECTUS OR TO REFLECT THE OCCURRENCE OF UNANTICIPATED EVENTS. ALL SUBSEQUENT WRITTEN AND ORAL FORWARD-LOOKING STATEMENTS ATTRIBUTABLE TO US OR PERSONS ACTING ON OUR BEHALF ARE EXPRESSLY QUALIFIED IN THEIR ENTIRETY BY THE CAUTIONARY STATEMENTS CONTAINED THROUGHOUT THIS PROSPECTUS OR IN ANY PROSPECTUS SUPPLEMENT OR IN THE INFORMATION INCORPORATED BY REFERENCE HEREIN OR THEREIN.

6

---

Table of Contents

THE COMPANY

        Our company was incorporated in Delaware in 2004 as Arpeggio Acquisition Corporation ("Arpeggio"), a specified purpose acquisition corporation. On June 28, 2006, Hill International, Inc. ("Old Hill"), a Delaware corporation, merged into Arpeggio, which was the surviving entity of the merger. Old Hill was founded in 1976 by Irvin E. Richter, our current Chairman and Chief Executive Officer. Immediately following the merger, the stockholders of Old Hill owned approximately 63.6% of the total voting power of Arpeggio. After the merger, Arpeggio changed its name to "Hill International, Inc."

        We currently provide project management and construction claims services to clients worldwide, but primarily in the United States, Latin America, Europe, the Middle East, North Africa, Asia and Australia. Our clients include the United States and other national governments and their agencies, state and local governments and their agencies and the private sector. We are organized into two key operating segments: the Project Management Group and the Construction Claims Group.

        In our Project Management Group, we provide construction management services which include program management, project management, construction management, project management oversight, troubled project turnaround, staff augmentation, estimating and cost management, project labor agreements and management consulting. In our Construction Claims Group, we advise clients in order to assist them in preventing or resolving claims and disputes based upon schedule delays, cost overruns and other problems on major construction projects worldwide.

        We are one of the leading firms in the world in both the project management and construction claims consulting businesses. We are a global company with approximately 3,000 personnel operating out of nearly 100 offices in more than 30 countries.

        Our executive office is located at 303 Lippincott Centre, Marlton, New Jersey 08053. We maintain a website at www.hillintl.com. The information contained on our website is not a part of, and is not incorporated by reference into, this prospectus. The telephone number at our executive office is (856) 810-6200.

RISK FACTORS

        Investing in shares of our common stock involves risk. Before making an investment decision, you should carefully consider the risks described under "Risk Factors" in the applicable prospectus supplement or other offering material and in our most recent Annual Report on Form 10-K, or any updates in our Quarterly Reports on Form 10-Q, together with all of the other information appearing in or incorporated by reference into this prospectus and any applicable prospectus supplement, in light of your particular investment objectives and financial circumstances. Our business, financial condition or results of operations could be materially adversely affected by any of these risks. The trading price of our shares of common stock could decline due to any of these or other risks, and you may lose all or part of your investment. For more information, see "Where You Can Find More Information."

USE OF PROCEEDS

        Unless indicated otherwise in the applicable prospectus supplement, we expect to use the net proceeds from the sale of shares of our common stock for our operations and for other general corporate purposes, including, but not limited to, capital expenditures, repayment or refinancing of borrowings, working capital, investments and acquisitions. We have not allocated any portion of the net proceeds for any particular use at this time. Pending such uses, we may invest the net proceeds in demand deposits, money market accounts or short-term, investment-grade, interest-bearing securities or guaranteed obligations of the United States government or other securities. Additional information on the use of net proceeds from the sale of securities offered by this prospectus may be set forth in the

7

---

Table of Contents

applicable prospectus supplement or other offering material relating to such offering. If net proceeds from a specific offering will be used to repay indebtedness, the applicable prospectus supplement or other offering material will describe the relevant terms of the debt to be repaid.

DESCRIPTION OF CAPITAL STOCK

        Our certificate of incorporation authorizes the issuance of 75,000,000 shares of common stock, par value $0.0001, and 1,000,000 shares of preferred stock, par value $0.0001. As of June 30, 2011, 38,493,703 shares of common stock were outstanding and no shares of preferred stock were outstanding.

Common Stock

        The holders of common stock are entitled to one vote for each share held of record on all matters to be voted on by stockholders. Our board of directors is divided into three classes, each of which will serve for a term of three years with only one class of directors being elected in each year. There is no cumulative voting with respect to the election of directors, with the result that the holders of more than 50% of the shares voted for the election of directors can elect all of the directors. Subject to the rights and preferences of any preferred stock which may be outstanding in the future, the holders of our common stock are entitled to equal dividends and distributions per share with respect to the common stock when and if declared by our board of directors from funds legally available therefor. In the event of our liquidation, dissolution or winding up, the holders of common stock are entitled to share ratably in all assets remaining after payment of liabilities, subject to the liquidation preferences of any preferred stock then outstanding. All shares of common stock now outstanding are fully paid, validly issued and non-assessable. Holders of our common stock do not have any conversion, preemptive or other subscription rights and there are no sinking fund or redemption provisions applicable to the common stock.

Preferred Stock

        Our certificate of incorporation authorizes the issuance of 1,000,000 shares of a "blank check" preferred stock with such designations, rights and preferences as may be determined from time to time by our board of directors. Accordingly, our board of directors is empowered, without stockholder approval, to issue preferred stock with dividend, liquidation, conversion, voting or other rights which could adversely affect the voting power or other rights of the holders of common stock. We may issue some or all of the preferred stock to effect a business combination or other acquisition transaction. In addition, the preferred stock could be utilized as a method of discouraging, delaying or preventing a change in control of the Company. The number of authorized shares of preferred stock may be increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of a majority of the voting power of all of the then outstanding shares of our capital stock entitled to vote generally in the election of directors, voting together as a single class, without a separate vote of the holders of the preferred stock, or any series thereof, unless a vote of any such holders is required pursuant to any preferred stock designation. There are no shares of preferred stock outstanding and we do not currently intend to issue any preferred stock.

Anti-Takeover Provisions

Delaware Law

        We are subject to Section 203 of the Delaware General Corporation Law regulating corporate takeovers, which prohibits a Delaware corporation from engaging in any business combination with an

8

---

Table of Contents

"interested stockholder" during the three-year period after such stockholder becomes an "interested stockholder," unless:

•

Prior to such time the stockholder became an interested stockholder, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;



•

The interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding (a) shares owned by persons who are directors and also officers, and (b) shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or



•

On or subsequent to the date of the transaction, the business combination is approved by the board of directors and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least 66²/3% of the outstanding voting stock which is not owned by the interested stockholder.

        Except as otherwise specified in Section 203, an "interested stockholder" is defined to include:

•

Any person that is the owner of 15% or more of the outstanding voting securities of the corporation, or is an affiliate or associate of the corporation and was the owner of 15% or more of the outstanding voting stock of the corporation at any time within three years immediately prior to the date of determination; and



•

The affiliates and associates of any such person.

Certificate of Incorporation and Bylaws

        Our amended and restated certificate of incorporation, or our certificate of incorporation, and amended and restated bylaws, or our bylaws, include provisions that:

•

Our board of directors is expressly authorized to make, alter or repeal our bylaws;



•

Our board of directors is divided into three classes of service with staggered three-year terms. This means that only one class of directors will be elected at each annual meeting of stockholders, with the other classes continuing for the remainder of their respective terms;



•

Our board of directors is authorized to issue preferred stock without stockholder approval;



•

Only our board of directors, Chairman of the Board, our Chief Executive Officer or the holders of a majority in amount of our capital stock issued and outstanding and entitled to vote may call a special meeting of stockholders; this means that minority stockholders cannot force stockholder consideration of a proposal, including a proposal to replace our board of directors, by calling a special meeting of stockholders prior to such time authorized by our board of directors, Chairman of the Board, our Chief Executive Officer or the holders of a majority in amount of our capital stock issued and outstanding and entitled to vote;



•

Our bylaws require advance notice for stockholder proposals and director nominations;



•

Our bylaws limit the removal of directors and the filling of director vacancies; and



•

We will indemnify officers and directors against losses that may incur in connection with investigations and legal proceedings resulting from their services to us, which may include services in connection with takeover defense measures.

        These provisions may make it more difficult for stockholders to take specific corporate actions and could have the effect of delaying or preventing a change in control of our company.

9

---

Table of Contents

PLAN OF DISTRIBUTION

        We may sell the shares of common stock from time to time in one or more transactions through underwriters or dealers, through agents, or directly to one or more purchasers, in private transactions, at a fixed price or prices, which may be changed, or from time to time at market prices prevailing at the time of sale, at prices related to the prevailing market prices, or at negotiated prices. We will describe the method of distribution and the terms of the offering of the shares of common stock in a prospectus supplement, information incorporated by reference or other offering material, including:

•

the name or names of the underwriters, if any;



•

the purchase price of the shares of common stock and the proceeds we will receive from the sale;



•

any underwriting discounts and other items constituting underwriters' compensation;



•

any initial public offering price;



•

any discounts or concessions allowed or reallowed or paid to dealers; and



•

any securities exchange or market on which the common stock may be listed.

        Only underwriters we name in the prospectus supplement, information incorporated by reference or other offering material are underwriters of the shares of our common stock offered thereby.

        If we use underwriters in the sale, they will acquire the shares of our common stock for their own account and may resell them from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase shares of our common stock will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the shares of our common stock to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all the shares of our common stock offered by the prospectus supplement, information incorporated by reference or other offering material. In connection with the sale of shares of our common stock, underwriters may receive compensation from us or from purchasers of shares of our common stock for whom they may act as agents. This compensation may be in the form of discounts, concessions or commissions.

        Underwriters may sell shares of our common stock to or through dealers, and these dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agents. Underwriters, dealers and agents that participate in the distribution of shares of our common stock could be considered underwriters, and any discounts or commissions received by them from us and any profit on the resale of shares of our common stock by them could be considered underwriting discounts and commissions, under the Securities Act. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time.

        If we sell shares of our common stock to a dealer, we will sell the shares of our common stock to the dealer, as principal. The name of the dealer and the terms of the transaction will be set forth in the prospectus supplement, information incorporated by reference or other offering material. The dealer may then resell the shares of our common stock to the public at varying prices to be determined by the dealer at the time of resale.

        We may sell shares of our common stock directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of shares of our common stock, and we will describe any commissions we will pay the agent, in the prospectus supplement, information

10

---

Table of Contents

incorporated by reference or other offering material. Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

        Under agreements entered into by us for the purchase or sale of shares of our common stock, underwriters, dealers and agents may be entitled to indemnification by us against certain liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which they may be required to make in respect thereof. Underwriters, dealers and agents may be customers of, engage in transactions with, or perform services for, us in the ordinary course of business.

        Offers to purchase shares of our common stock may be solicited, and sales thereof may be made, by us directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act with respect to any resales of those shares of our common stock. The terms of any such offer will be set forth in the prospectus supplement, information incorporated by reference or other offering material.

        If we offer shares of our common stock in a subscription rights offering to our existing security holders, we may enter into a standby underwriting agreement with dealers, acting as standby underwriters. We may pay the standby underwriters a commitment fee for the shares of our common stock they commit to purchase on a standby basis. If we do not enter into a standby underwriting arrangement, we may retain a dealer-manager to manage a subscription rights offering for us.

        If so indicated in the prospectus supplement, we will authorize the underwriters or other persons acting as our agents to solicit offers by certain institutional investors to purchase shares of our common stock from us under contracts requiring payment and delivery on a future date. The obligations of any purchaser under these contracts will be subject to the condition that the purchase of the offered shares of our common stock shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that purchaser is subject. The underwriters and other agents will not have any responsibility in respect of the validity or performance of these contracts.

        To the extent that we make sales to or through one or more underwriters or agents in at-the-market offerings, we may do so pursuant to the terms of a distribution agreement between us and the underwriters or agents. If we engage in at-the-market sales pursuant to a distribution agreement, we will issue and sell shares of our common stock to or through one or more underwriters or agents, which may act on an agency basis or on a principal basis. During the term of any such agreement, we may sell shares on a daily basis in exchange transactions or otherwise as we may agree with the underwriters or agents. The distribution agreement will provide that any shares of our common stock sold will be sold at prices related to the then prevailing market prices for our common stock. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined at this time and will be described in a prospectus supplement. Pursuant to the terms of the distribution agreement, we also may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase, blocks of our common stock. The terms of each such distribution agreement will be set forth in more detail in a prospectus supplement to this prospectus. In the event that any underwriter or agent acts as principal, or broker-dealer acts as underwriter, it may engage in certain transactions that stabilize, maintain or otherwise affect the price of our common stock. We will describe any such activities in the prospectus supplement relating to the transaction.

        In connection with an offering, the underwriters may purchase and sell securities in the open market. These transactions may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of shares of our common stock than they are required to purchase in an offering. Stabilizing transactions consist of certain bids or purchases made for the purpose of preventing or retarding a decline in the market price of our common stock while an offering is in progress.

11

---

Table of Contents

        The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the underwriters have repurchased shares of our common stock sold by or for the account of that underwriter in stabilizing or short-covering transactions.

        These activities by the underwriters may stabilize, maintain or otherwise affect the market price of the shares of our common stock. As a result, the price of the shares of our common stock may be higher than the price that otherwise might exist in the open market. If these activities are commenced, they may be discontinued by the underwriters at any time. These transactions may be effected on an exchange or automated quotation system, if the shares of our common stock are listed on that exchange or admitted for trading on that automated quotation system, or in the over-the-counter market or otherwise.

        In compliance with guidelines of the Financial Industry Regulatory Authority, or FINRA, the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and any applicable prospectus supplement.

LEGAL MATTERS

        Unless otherwise specified in the applicable prospectus supplement, the validity of any shares of our common stock issued hereunder will be passed upon for our company by Duane Morris LLP, Philadelphia, Pennsylvania, and for any underwriters or agents by counsel named in the applicable prospectus supplement.

EXPERTS

        The consolidated financial statements of Hill International, Inc. at December 31, 2009 and for each of the years in the two-year period ended December 31, 2009 have been audited by Amper, Politziner & Mattia, LLP, independent registered public accounting firm, as set forth in their report incorporated by reference herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

        On August 16, 2010, we were notified that Amper, Politziner & Mattia, LLP combined its practice with that of Eisner LLP and the name of the combined practice operates under the name EisnerAmper LLP and that Amper, Politziner & Mattia, LLP resigned as our independent registered public accounting firm. At that time, EisnerAmper LLP was appointed as our new independent registered public accounting firm. The consolidated financial statements of Hill International, Inc. at December 31, 2010 and for the year ended December 31, 2010 have been audited by EisnerAmper LLP, independent registered public accounting firm, as set forth in their report incorporated by reference herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

        The financial statements of Stanley Baker Hill, LLC at December 31, 2009 and for the year then ended have been audited by Schneider Downs & Co., Inc., independent registered public accounting firm, as set forth in their report incorporated by reference herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

12

---

Table of Contents

8,000,000 Shares

Common Stock

P R E L I M I N A R Y    P R O S P E C T U S    S U P P L E M E N T

KeyBanc Capital Markets

William Blair
Houlihan Lokey
Boenning & Scattergood, Inc.
Sidoti & Company, LLC
SOCIETE GENERALE

                        , 2014

   

---