AMENDMENT NO. 1 TO AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT

Exhibit 10.1

AMENDMENT NO. 1 TO AMENDED AND RESTATED CREDIT AGREEMENT

THIS AMENDMENT NO. 1 TO AMENDED AND RESTATED CREDIT AGREEMENT (this “Amendment”) is made as of February 25, 2005, by and among CARRAMERICA REALTY OPERATING PARTNERSHIP, L.P., a Delaware limited partnership (the “Borrower”), CARRAMERICA REALTY CORPORATION and CARRAMERICA REALTY L.P., as Guarantors (the “Guarantors”), the BANKS listed on the signature pages hereof, JPMORGAN CHASE BANK, N.A. (successor to JPMorgan Chase Bank), as Administrative Agent, J.P. MORGAN SECURITIES INC., as Lead Arranger and Sole Bookrunner, BANK OF AMERICA, N.A., as Syndication Agent, and PNC BANK, NATIONAL ASSOCIATION, WACHOVIA BANK, NATIONAL ASSOCIATION, and WELLS FARGO BANK, NATIONAL ASSOCIATION, as documentation Agent, and COMMERZBANK AG, NEW YORK BRANCH, NATIONAL AUSTRALIA BANK LIMITED, NEW YORK BRANCH and US BANK, as Co-Agents.

W I T N E S S E T H:

WHEREAS, the Borrower and the Banks have entered into the Amended and Restated Revolving Credit Agreement, as of June 30, 2004 (the “Credit Agreement”); and

WHEREAS, the parties desire to modify the Credit Agreement upon the terms and conditions set forth herein.

NOW THEREFORE, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties do hereby agree as follows:

1. Definitions. All capitalized terms not otherwise defined herein shall have the meanings ascribed to them in the Credit Agreement.

2. FMV Cap Rate. The definition of “FMV Cap Rate” is hereby deleted and the following substituted therefor: “‘FMV Cap Rate’ means 9% except that with respect to those properties located in the following counties or cities, it shall mean 8.5%: Montgomery County, MD, Prince George’s County, MD, Washington, D.C., Arlington, VA, Alexandria, VA,, Fairfax County, VA, Loudoun County, VA.”

3. Maximum Total Debt Ratio. Section 5.8(b)is hereby amended by deleting the reference to “55%” and substituting “60%” therefor.

4. Effective Date. This Amendment shall become effective upon receipt by the Administrative Agent of counterparts hereof signed by the Borrower and the Required Banks (the date of such receipt being deemed the “Effective Date”).

5. Representations and Warranties. Borrower hereby represents and warrants that as of the Effective Date, all the representations and warranties set forth in the Credit Agreement, as amended hereby, are true and complete in all material respects.

6. Entire Agreement. This Amendment constitutes the entire and final agreement among the parties hereto with respect to the subject matter hereof and there are no other agreements, understandings, undertakings, representations or warranties among the parties hereto with respect to the subject matter hereof except as set forth herein.

7. Governing Law. This Amendment shall be governed by, and construed in accordance with, the law of the State of New York.

8. Counterparts. This Amendment may be executed in any number of counterparts, all of which taken together shall constitute one and the same agreement, and any of the parties hereto may execute this Amendment by signing any such counterpart.

9. Headings, Etc. Section or other headings contained in this Amendment are for reference purposes only and shall not in any way affect the meaning or interpretation of this Amendment.

10. No Further Modifications. Except as modified herein, all of the terms and conditions of the Credit Agreement, as modified hereby shall remain in full force and effect and, as modified hereby, the Borrower confirms and ratifies all of the terms, covenants and conditions of the Credit Agreement in all respects.

IN WITNESS WHEREOF, this Agreement has been duly executed as of the date first above written.