<PAGE>

                                                             Exhibit 10(x)(x)(x)

                                 AMENDMENT TO
                       PERFORMANCE SHARE AWARD AGREEMENT

     This Amendment to Performance Share Award Agreement (this "Amendment") is
made as of February 25, 2000, between Federal Realty Investment Trust, a
Maryland real estate investment trust (the "Trust"), and Steven J. Guttman, an
individual employee of the Trust (the "Key Employee").

     WHEREAS, the Trust and the Key Employee entered into that certain
Performance Share Award Agreement dated as of January 1, 1998 (the "Performance
Share Agreement") setting forth the terms of the award by the Trust to the Key
Employee under the Trust's Amended and Restated 1993 Long-Term Incentive Plan
(the "Amended Plan") of a Performance Share Award of 300,000 shares of
beneficial interest of the Trust (the "Performance Shares"); and

     WHEREAS, the Performance Share Agreement provided for the Performance
Shares to vest according to the attainment of certain fixed performance target
levels set forth therein (the "Performance Target"); and

     WHEREAS, the Compensation Committee of the Board of Trustees of the Trust
(the "Committee") has determined that the Performance Target, rather than
remaining at a fixed level for the entire term of the Agreement, should be
established annually by the Committee at the beginning of each year in order to
better align the Key Employee's financial incentives under the Agreement with
successful execution of the Trust's business plan for that year.

     NOW, THEREFORE, in consideration of the foregoing, the mutual promises
herein contained and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto, intending to be
legally bound hereby, agree as follows:

     1.   Paragraph 4.2(b) of the Performance Share Agreement is hereby amended
to read in its entirety as follows:

          "Beginning with the Award Period commencing on January 1, 2000, the
          Performance Target will have been met or exceeded based upon the
          application of an annual test, which shall meet the criteria set forth
          in Section 8.01(a) of the Amended Plan. The Committee shall establish
          both a threshold level, the attainment of which shall result in the
          Restriction Period lapsing as to 37,500 Performance Shares, and a
          maximum level, the attainment of which will result in the Restriction
          Period lapsing as to 60,000 Performance Shares. The Performance Target
          (both the threshold level and the maximum level) for the 2000 Award
          Period is attached to this
<PAGE>

          Agreement, and the Performance Target for each subsequent Award Period
          shall be attached to this Agreement as it is established by the
          Committee. In the event that the Committee fails to establish a
          Performance Target for an Award Period during the first calendar
          quarter of such Award Period, the Performance Target for the prior
          Award Period shall be deemed to apply. If, in any Award Period, the
          Trust does not meet or exceed the Performance Target (after taking
          into account the lapsing of Performance Shares resulting therefrom),
          the Restriction Period will not lapse as to any Performance Shares
          allocable to such Award Period."

     2.   Appendix A to the Performance Share Agreement is hereby deleted in its
entirety, as is the reference in Paragraph 4.2(a) to Appendix A.

     3.   Capitalized terms used in this Amendment, unless otherwise defined
herein, have the respective meanings given to such terms in the Performance
Share Agreement.

     4.   Except as specifically modified hereby, the Performance Share
Agreement remains in full force and effect, and the Trust and the Key Employeee
hereby ratify and reaffirm each and all of the terms and provisions of the
Performance Share Agreement as modified hereby.

     5.   This Amendment may be executed in multiple counterparts with the same
effect as if each of the signing parties had signed the same document. All
counterparts shall be construed together and constitute the same instrument.

                                      -2-
<PAGE>

     IN WITNESS WHEREOF, the Trust has caused this Amendment to be duly executed
and the Key Employee has hereunto set his hand effective as of the day and year
first above written.

                                        FEDERAL REALTY INVESTMENT TRUST

                                        By: /s/ Walter F. Loeb
                                           __________________________________
                                        Name: Walter F. Loeb
                                        Title:  Chair, Compensation Committee

                                        Address:
                                        1626 East Jefferson Street
                                        Rockville, Maryland 20852


                                        STEVEN J. GUTTMAN

                                         /s/  Steven J. Guttman
                                        _____________________________________

                                        Address:
                                        5126 Wissioming Road
                                        Bethesda, Maryland 20816

                                      -3-
<PAGE>

            ATTACHMENT TO GUTTMAN PERFORMANCE SHARE AWARD AGREEMENT


                   Performance Target for 2000 Award Period
                   ----------------------------------------

<TABLE>
<CAPTION>
             Funds From Operations/Annual                  Number of Performance Shares as to which
               Per Share Growth Rate/1/                            Restriction Period Lapses
<S>                                                        <C>
                     Less than 5%                                            None
Threshold level:  Equal to or greater than 5% but less                   37,500 shares
                        than 7%
      Maximum level:  Equal to or greater than 7%                        60,000 shares
</TABLE>


______________________

/1/ As the same may be adjusted for specific items as agreed between the
Committee and the Key Employee.

                                      -4-