UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C.  20549

                            SCHEDULE 14A INFORMATION

          Proxy Statement Pursuant to Section 14(a) of the Securities
                    Exchange Act of 1934 (Amendment No.   )

                          Filed by the Registrant [X]

                 Filed by a Party other than the Registrant [ ]

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   [ ]  Preliminary Proxy Statement         [ ]  CONFIDENTIAL, FOR USE OF THE
                        COMMISSION ONLY (AS PERMITTED BY
                               RULE 14A-6(E)(2))

                        [ ]  Definitive Proxy Statement

                      [X]  Definitive Additional Materials

[ ]  Soliciting Material Pursuant to Section 240.14a-11(c) or Section 240.14a-12


                         ICF Kaiser International, Inc.
                         ------------------------------
                (Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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[ ]  Fee paid previously with preliminary materials.

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Notes:


                [LETTERHEAD OF ICF KAISER INTERNATIONAL, INC.]

                               October 20, 1999

                          YOUR VOTE IS VERY IMPORTANT

                      -----------------------------------

Dear Fellow Shareholders:

You have previously received proxy materials in connection with the Annual
Meeting of Shareholders of ICF Kaiser International, Inc. to be held on
Thursday, November 4, 1999. According to our latest records, your PROXY VOTE
for this meeting HAS NOT BEEN RECEIVED.

At this meeting you are being asked to approve several proposals, which
relate, among other things, to a debt restructuring that is described fully in
the Proxy Statement. These proposals are very important to our efforts to
reposition Kaiser and create the opportunity for long-term value for you, our
shareholders.

WE NEED YOUR SUPPORT! Several proposals require a majority of the outstanding
shares for approval and Proposal 4 (the Shareholder Democracy Proposal)
requires the affirmative vote of two-thirds of the outstanding shares. If you
do not vote, it is as if you are opposing these proposals. Your broker allows
you to vote your shares telephonically or via the internet if you wish. Follow
the instructions on the enclosed voting form to cast your ballot. Remember,
your broker cannot vote your shares until you instruct him or her to do so.

You may vote by any of the following methods:

 .  Call the toll-free 800# on the voting form included in this package. This
   call will not cost you anything. Using your 12-digit control number located
   on the voting form, cast your ballot.

 .  Vote over the internet at www.proxyvote.com using the 12-digit control
   number located on the voting form.

 .  Sign the proxy and mail it back in the enclosed postage-paid envelope prior
   to the meeting date.

Thank you for your support.

                                        Sincerely,


                                        /s/ James J. Maiwurm
                                        -------------------------------
                                        James J. Maiwurm
                                        Chairman, President and Chief
                                        Executive Officer