PROSPECTUS SUPPLEMENT
(To Prospectus Dated January 28, 1998)


                               OMNICOM GROUP INC.
                        1,000,000 Shares of Common Stock
                                ($.15 Par Value)

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      This document supplements the Prospectus dated January 28, 1998 relating
to 1,000,000 shares of Common Stock, par value $.15 per share (the "Common
Stock") of the Omnicom Group Inc., a New York corporation ("Omnicom" or the
"Company"). Each share of Common Stock offered hereby was issued upon exchange
of an Exchangeable Share (an "Exchangeable Share") of Omnicom Canada Inc.
("OCI"), a corporation incorporated under the laws of Ontario and a wholly-owned
subsidiary of the Company, originally issued in a private offering in Canada by
OCI for the Class A Common Shares and Class B Common Shares of Quintenco
Holdings Inc., a corporation (now amalgamated with OCI) under the laws of
Ontario ("QHI"), in connection with the combination of OCI and QHI. This
Prospectus Supplement is incorporated by reference into the Prospectus, and all
terms used herein shall have the meaning assigned to them in the Prospectus. On
February 23, 2001, the closing price of the Common Stock as reported on the New
York Stock Exchange was $90.20 per share. The Common Stock is traded under the
symbol "OMC."


      The Selling Shareholders do not own in excess of 1% of the Common Stock of
the Company and since the Selling Shareholders may sell all, some or none of the
shares of Common Stock offered hereby, no estimate can be made of the aggregate
number of shares of Common Stock that will be owned by the Selling Shareholders
upon completion of the offering to which this Prospectus Supplement relates. In
accordance with the Section of the Prospectus entitled "Selling Shareholders"
(which appears on page 10 of the Prospectus), the following information is
provided with respect to the beneficial owners of the Common Stock:



                                                           Amount of Shares               Amount of
                                                          Beneficially Owned            Shares to be
          Name of Selling Shareholder(s)                as of February 23, 2001       Offered for Sale
          ------------------------------                -----------------------       ----------------
                                                                                     
          1222288 Ontario Inc.                                  50,000                     50,000
          John Campbell Reston                                  10,000                     10,000


      Except for the purchase of the shares of Common Stock, the Selling
Shareholders have not had a material relationship with the Company or any of its
affiliates within the past three years.




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THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITY COMMISSION NOR HAS THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE ACCURACY
OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL
OFFENSE.

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          The date of this Prospectus Supplement is February 28, 2001.