Filed Pursuant to Rule 424(b)(3)
Registration No. 333-100244

March 5, 2004

Prospectus Supplement No. 1
To Reoffer Prospectus, Dated July 10, 2003

of

MACK-CALI REALTY CORPORATION

Relating to

213,529 Shares of Common Stock of Mack-Cali Realty Corporation

        This prospectus supplement, dated March 5, 2004 (this “Supplement”), supplements our reoffer prospectus filed as part of our Post Effective Amendment No. 1 to Registration Statement on Form S-8 dated July 10, 2003 (the “Prospectus”), relating to the resale by certain of our shareholders (collectively, the “Selling Shareholders”) who have acquired our common stock, par value $.01 per share, offered by this Supplement in conjunction with the Prospectus pursuant to our 2000 Employee Stock Option Plan or our Amended and Restated 2000 Director Stock Option Plan (collectively, the “Plans”). This Supplement presents certain information regarding the ownership of our common stock by the Selling Shareholders as of February 16, 2004, and updates the number of shares of our common stock available for resale by each Selling Shareholder pursuant to the Plans. No additional securities are being registered hereby.

        You should read this Supplement in conjunction with the Prospectus. This Supplement is qualified by reference to the Prospectus, except to the extent the information in this Supplement supersedes the information contained in the Prospectus.

SELLING SHAREHOLDERS

        The Selling Shareholders are persons listed in the table below who have acquired the common stock offered by this Supplement in conjunction with the Prospectus pursuant to our 2000 Employee Stock Option Plan or our Amended and Restated 2000 Director Stock Option Plan. Each Selling Shareholder will receive all of the net proceeds from the sale of his shares of common stock offered by this Supplement in conjunction with the Prospectus.

        The following table presents certain information regarding the ownership of our common stock by the Selling Shareholders as of February 16, 2004. The number of shares of common stock outstanding will not change as a result of the offering, nor will the number of shares owned or percentage of ownership of any persons other than the Selling Shareholders change as a result thereof. However, because the Selling Shareholders may offer from time to time all or some of their shares under this Supplement, or in another permitted manner, no assurances can be given as to the actual number of shares that will be sold by the Selling Shareholders or that will be held by the Selling Shareholders after completion of the sales.

        The information contained in the following table is as of February 16, 2004, and supersedes and replaces the table of Selling Shareholders, and the related footnotes, contained in the Prospectus.

Name and Position With Us
Number of
Shares Owned
Prior to
Offering(1)

Number of
Shares
Registered
Hereby(2)

Number of
Shares to Be
Owned After
Offering(3)

William L. Mack   3,310,384   1,500   3,308,884  
Chairman of the Board 
  
Mitchell E. Hersh  296,372   52,448   243,924  
Chief Executive Officer and Director 
  
Timothy M. Jones  361,344   59,269   302,075  
President 
  
Barry Lefkowitz  106,919   27,469   79,450  
Executive Vice President and Chief Financial Officer 
  
Roger W. Thomas  98,885   27,224   71,661  
Executive Vice President, General Counsel and Secretary 
  
Michael A. Grossman  74,101   24,619   49,482  
Executive Vice President 
  
Martin S. Berger  544,032   1,500   542,532  
Director 
  
Brendan T. Byrne  32,100   1,500   30,600  
Director 
  
John R. Cali  259,311   1,500   257,811  
Director 
  
Nathan Gantcher  53,500   1,500   52,000  
Director 
  
Martin D. Gruss  34,500   1,500   33,000  
Director 
  
David S. Mack  2,272,947   6,000   2,266,947  
Director 
  
Earle I. Mack  2,219,354   1,500   2,217,854  
Member of the Advisory Board 
  
Alan G. Philibosian  35,000   1,500   33,500  
Director 
  
Irvin D. Reid  6,500   1,500   5,000  
Director 
  
Vincent Tese  41,500   1,500   40,000  
Director 
  
Roy J. Zuckerberg  46,500   1,500   45,000  
Director 

(1) Includes shares of common stock acquired not pursuant to any employee or director benefit plan, common stock underlying options and restricted stock granted pursuant to our 2000 Employee Stock Option Plan and our Amended and Restated 2000 Director Stock Option Plan (both vested and unvested), common stock underlying options granted pursuant to any other employee or director benefit plan, restricted stock granted under any other employee or director benefit plan, and common stock underlying common units, preferred units (as converted into common units), and vested warrants to acquire common stock.

(2) Includes all common stock underlying options granted and outstanding as of February 16, 2004 (both vested and unvested), and all restricted stock issued, pursuant to our 2000 Employee Stock Option Plan and our Amended and Restated 2000 Director Stock Option Plan.

(3) Assumes all shares registered under this prospectus will be sold.

        If and when a selling shareholder sells all of his shares of common stock registered under this Supplement, the following Selling Shareholders will own more than one percent of our common stock at February 16, 2004:


Name
Percentage
Ownership

William L. Mack   4 .44
David S. Mack  3 .04
Earle I. Mack  2 .97

        Information concerning the Selling Shareholders may change from time to time and will be set forth in future supplements. Accordingly, the number of shares of our common stock offered hereby may increase or decrease. Full and complete copies of this Supplement and the Prospectus will be provided upon request.