FILED PURSUANT TO RULE 424(B)(3)
                                                      REGISTRATION NO. 333-86194

                                  $900,000,000

                               OMNICOM GROUP INC.
               Zero Coupon Zero Yield Convertible Notes Due 2032

                   PROSPECTUS SUPPLEMENT DATED AUGUST 12, 2003
                        TO PROSPECTUS DATED JUNE 3, 2002

      The selling securityholders table on pages 32-33 of the prospectus is
hereby further amended to update the information to include the following entity
as a selling securityholder in the prospectus and to list its total amount of
Zero Coupon Zero Yield Convertible Notes due 2032:



                                        AGGREGATE
                                     PRINCIPAL AMOUNT                           COMMON            COMMON
                                       OF NOTES AT         PERCENTAGE           STOCK             STOCK
                                      MATURITY THAT         OF NOTES        OWNED PRIOR TO      REGISTERED
NAME                                   MAY BE SOLD         OUTSTANDING        CONVERSION         HEREBY(1)
----                                 ----------------      -----------      --------------      ----------
                                                                                      
Merrill Lynch International
  Limited(2)(3)                         $10,000,000           1.1%                --              90,900


----------
(1)   Assumes conversion of all the holder's notes at a conversion rate of 9.09
      shares of common stock per $1,000 principal amount at maturity of the
      notes. However, this conversion rate will be subject to adjustment as
      described under "Description of the Notes -- Conversion Rights." As a
      result, the amount of common stock issuable upon conversion of the notes
      may increase or decrease in the future.

(2)   This selling securityholder was previously listed as holding $40,000,000
      of the notes. This information supersedes all prior information regarding
      Merrill Lynch International Limited.

(3)   Merrill Lynch, Pierce Fenner & Smith Incorporated has advised us that it
      is not aware of any position, office or directorship relationship with
      Omnicom or its affiliates. However, Merrill Lynch has advised us that it
      may have from time to time acted in a financial investment advisory
      capacity to Omnicom.

      The preceding table has been prepared based upon information furnished to
us by the selling securityholders named in the table. From time to time,
additional information concerning ownership of the notes and common stock may be
known by certain holders thereof not named in the preceding table, with whom we
believe we have no affiliation. Information about the selling securityholders
may change over time. Any changed information will be set forth in supplements
of amendments to this prospectus.