<PAGE>

                                                                    EXHIBIT 32.1

                            OFFICERS' CERTIFICATIONS

                    CERTIFICATION OF CHIEF EXECUTIVE OFFICER

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                By:  /s/  Richard S. Ziman
                                         ------------------------------------
                                         Richard S. Ziman
                                         Chairman of the Board and
                                         Chief Executive Officer
                                         Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

<PAGE>

                    CERTIFICATION OF CHIEF FINANCIAL OFFICER

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                By:  /s/  Richard S. Davis
                                         ------------------------------------
                                         Richard S. Davis
                                         Senior Vice President and
                                         Chief Financial Officer
                                         Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

<PAGE>

                    CERTIFICATION OF CHIEF OPERATING OFFICER

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                     By:  /s/ Victor J. Coleman
                                              -------------------------
                                              Victor J. Coleman
                                              President and
                                              Chief Operating Officer
                                              Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

<PAGE>

                    CERTIFICATION OF EXECUTIVE VICE PRESIDENT

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                By:  /s/  Andrew J. Sobel
                                         ------------------------------------
                                         Andrew J. Sobel
                                         Executive Vice President,
                                         Strategic Planning and Operations
                                         Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

<PAGE>

                     CERTIFICATION OF SENIOR VICE PRESIDENT

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                     By:  /s/  Robert C. Peddicord
                                              ---------------------------------
                                              Robert C. Peddicord
                                              Senior Vice President,
                                              Leasing and Property Operations
                                              Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.

<PAGE>

                        CERTIFICATION OF GENERAL COUNSEL

Pursuant to 18 U.S.C. Section 1350, as created by Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned officer of Arden Realty, Inc. (the
"Company"), hereby certifies, to such officer's knowledge, that:

      (i)   the accompanying quarterly report on Form 10-Q of the Company for
            the period ended June 30, 2004 (the "Report") fully complies with
            the requirements of Section 13(a) or Section 15(d), as applicable,
            of the Securities Exchange Act of 1934, as amended; and

      (ii)  the information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

Date: August 6, 2004                By:  /s/  David A. Swartz
                                         ------------------------------------
                                         David A. Swartz
                                         General Counsel and
                                         Secretary
                                         Arden Realty, Inc.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished solely to accompany the Report
pursuant to 18 U.S.C. Section 1350, and is not being filed for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be
incorporated by reference into any filing of the Company, whether made before or
after the date hereof, regardless of any general incorporation language in such
filing.