PROSPECTUS SUPPLEMENT
(To Prospectus Dated May 4, 2000)

                               OMNICOM GROUP INC.
                         110,000 Shares of Common Stock
                                ($.15 Par Value)

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      This document  supplements  the  Prospectus  dated May 4, 2000 relating to
110,000 shares of common stock,  par value $.15 per share (the "Common  Stock"),
of the Omnicom Group Inc., a New York corporation (the "Company"). Each share of
Common  Stock  offered  hereby was issued upon the  exchange of an  exchangeable
share (an "Exchangeable  Share") of TAI Acquisition Inc. ("TAI"),  a corporation
organized  under the laws of the  Province of Ontario.  TAI issued  Exchangeable
Shares to the selling  shareholders,  all of whom are  residents  of Canada,  as
partial  consideration  for the  common  shares,  preference  shares and Class A
preference shares of Tudhope Associates Inc., a corporation  organized under the
laws of the  Province of Ontario  ("Tudhope").  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 28, 2001, the
closing price of the Common Stock as reported on the New York Stock Exchange was
$90.69 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 7 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 28, 2001   Offered for Sale
 ------------------------------     -----------------------   ----------------
 Beverley W. Tudhope                        11,694                 11,694
 Ian C. Tudhope                             11,694                 11,694

      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 March 5, 2001.