PROSPECTUS SUPPLEMENT
(To Prospectus Dated May 4, 2000)

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

                                   ----------

      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 January 5, 2004,  the
closing price of the Common Stock as reported on the New York Stock Exchange was
$87.88 per share. The Common Stock is traded under the symbol "OMC."

      The Selling  Shareholder  does not own in excess of 1% of the Common Stock
of the Company and since the Selling  Shareholder  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
Shareholder 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     as of January 5, 2004     Offered for Sale
      ---------------------------     ---------------------     ----------------
      Ian C. Tudhope                         15,340                  15,340

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

                                   ----------

      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.

                                   ----------

           The date of this Prospectus Supplement is January 9, 2004.