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

SCHEDULE 14A

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

Filed by the Registrant   þ

Filed by a Party other than the Registrant   o

Check the appropriate box:

o   Preliminary Proxy Statement

o   Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

o   Definitive Proxy Statement

þ   Definitive Additional Materials

o   Soliciting Material Pursuant to §240.14a-12

WM. WRIGLEY JR. COMPANY

(Name of Registrant as Specified In Its Charter)

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

      Payment of Filing Fee (Check the appropriate box):

þ   No fee required.

o   Fee computed on table below per Exchange Act Rules 14a-6(i)(4) and 0-11.

      1) Title of each class of securities to which transaction applies:

      2) Aggregate number of securities to which transaction applies:

      3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined):

      4) Proposed maximum aggregate value of transaction:

      5) Total fee paid:

      o   Fee paid previously with preliminary materials.

      o   Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

      1) Amount Previously Paid:

      2) Form, Schedule or Registration Statement No.:

      3) Filing Party:

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SEC 1913 (02-02) Persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Wm. WRIGLEY Jr. Company

Wrigley Building       •       410 North Michigan Avenue       •       Chicago, Illinois 60611

March 22, 2006

Dear Stockholder:

      We have previously sent to you proxy materials for the Annual Meeting to be held on April 4, 2006. Included with these materials was a proxy card for stockholders to vote on each of the six matters described in the proxy materials.

      One of the matters that stockholders are to vote on is Proposal 5, which is an amendment to Article FOURTH of the Restated Certificate of Incorporation to defer, and permit the Board of Directors to further defer, the automatic conversion of Class B Common Stock if the automatic conversion threshold is crossed. The New York Stock Exchange advised the Company on March 16, 2006 that it would like the Company to modify Proposal 5.

      The accompanying Supplement to Proxy Statement describes the amendment to Article FOURTH, as modified, that is to be considered and acted upon by the stockholders.

      If you have already voted on the six matters described in the proxy materials and do not wish to change your vote, you do not need to take any action and your original vote will be counted. If you have already voted on the six matters described in the proxy materials and wish to change your vote, you may do so by using the enclosed new proxy card or by voting over the phone or Internet as described in the proxy statement mailed to you on or about February 16, 2006. I look forward to seeing you at the meeting.

Sincerely,

WILLIAM WRIGLEY, JR

Chairman of the Board, President

and Chief Executive Officer

SUPPLEMENT TO PROXY STATEMENT

FOR THE

103rd ANNUAL MEETING OF STOCKHOLDERS OF

WM. WRIGLEY JR. COMPANY

TO BE HELD ON TUESDAY, APRIL 4, 2006

      This Supplement (this “Supplement”) to the Proxy Statement, dated February 16, 2006 (the “Proxy Statement”), of Wm. Wrigley Jr. Company (the “Company”) is furnished in connection with the solicitation by the Board of Directors (the “Board”) of proxies to be voted at the Annual Meeting of Stockholders of the Company to be held at 9:00 a.m. Chicago time on Tuesday, April 4, 2006, at the Chase Auditorium, Chase Tower in Chicago, Illinois.

      This Supplement is dated March 22, 2006 and is first being mailed to stockholders on or about March 22, 2006.

      This Supplement is being distributed to provide stockholders with supplemental information regarding Proposal 5 (the “Proposal”) contained in the Proxy Statement. The Proposal, as described in the Proxy Statement, is an amendment to the Company’s Restated Certificate of Incorporation to provide that the conversion of Class B Common Stock into Common Stock will occur eighteen (18) months after the date on which the conversion threshold is crossed, which is referred to as the “determination period,” unless during the determination period the Board, based upon the recommendation of a committee of the Board comprised of not less than three (3) directors, all of whom shall be independent (the “Independent Committee”), shall have determined that the Class B Common Stock shall not convert on such 18-month anniversary, but instead shall convert at such time and/or under such circumstances as determined by the Board to be in the best interests of the Company and its stockholders. Based upon communications with the New York Stock Exchange (the “NYSE”), we have agreed to modify the Proposal so that if the determination were made to defer the conversion of the Class B Common Stock beyond the determination period, prior to each anniversary following the expiration of the determination period, if applicable, the Independent Committee will review and confirm that further deferral of the conversion time remains in the best interests of the Company and its stockholders. In no event will the conversion time be deferred for more than five (5) years after the expiration of the determination period.

      Article FOURTH, Section 2, Paragraph (d)(8) of the Restated Certificate of Incorporation is set out in Appendix A to this Supplement. Such Paragraph (d)(8) reflects the amendments contemplated by the Proposal, as modified. The modifications agreed with the NYSE are set forth in bold type.

      The Board of Directors determined that the Proposal, as modified, is advisable and in the best interests of the Company and all its stockholders. The Board of Directors approved the Proposal, as modified, and recommends that stockholders vote FOR the approval of the Proposal, as modified.

      Enclosed with this Supplement is a new proxy card, which is identical to the proxy card enclosed with the Proxy Statement. If you have already voted on the six matters described in the Proxy Statement, including the Proposal, and do not wish to change your vote due to the modification of the Proposal, you do not need to take any action and your original vote will be counted. If you have already voted on the six matters described in the Proxy Statement and wish to change your vote, you may do so by using the enclosed new proxy card or by voting over the phone or Internet as described in the Proxy Statement.

Howard Malovany,

Vice President, Secretary and General Counsel

Chicago, March 22, 2006

Appendix A

Article FOURTH, Section 2, Paragraph (d)(8)

      At any time when the aggregate number of outstanding shares of Class B Common Stock beneficially owned by the holders of Class B Common Stock, as reflected on the stock transfer records of the Corporation, falls below twelve percent (12%) of the aggregate number of the then outstanding shares of Common Stock and Class B Common Stock, each share of Class B Common Stock shall convert into one fully paid and non-assessable share of Common Stock on the 18 month anniversary of such time (or, if such 18 month anniversary is a day other than a business day, then such conversion shall occur on the next business day), unless prior to such conversion time the Board of Directors, based upon a recommendation of a committee of the Board of Directors comprised of not less than three directors, all of whom shall be independent directors of the Board of Directors, makes a determination (the “Board Determination”) that the Class B Common Stock shall not so convert, in which case the Class B Common Stock (i) shall not so convert pursuant to this subdivision (d)(8) on such 18 month anniversary and (ii) shall so convert pursuant to this subdivision (d)(8) only at such time and/or under such circumstances (which may, if so provided in the Board Determination, include a subsequent determination to be made by a committee of the Board of Directors comprised of not less than three independent directors on the Board of Directors) as shall be specified in the Board Determination, provided, however, that if the Board Determination provided for a deferral of the conversion of the Class B Common Stock beyond such 18 month anniversary, prior to each anniversary following the expiration of such 18 month period, if applicable, a committee of the Board of Directors comprised of not less than three independent directors of the Board of Directors shall review the Board Determination and confirm that further deferral of the conversion time remains in the best interests of the Company and its stockholders, provided, further, that in no event shall such conversion time be deferred for more than five (5) years after the expiration of such 18 month period. The Corporation shall promptly make a public announcement of any Board Determination. For purposes of this subdivision (d)(8), the total number of shares of Common Stock and Class B Common Stock “outstanding” at any time shall not include any shares of Common Stock which, after April 1, 1986, are (a) issued in exchange for the assets or stock of other entities (including pursuant to a merger or other business combination), (b) sold by the Corporation for value, (c) issued upon conversion of convertible securities issued in exchange for the assets or stock of other entities or sold by the Corporation for value, or (d) issued as a stock split or dividend with respect to shares issued or sold pursuant to clause (a), (b) or (c). For purposes of the first sentence of this subdivision (d)(8), any shares of Common Stock repurchased by the Corporation shall no longer be deemed “outstanding” from and after the date of repurchase.