Securities and Exchange Commission

Amendment No. 1
to Form 10-K on

þ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES AND EXCHANGE ACT OF 1934.

For the fiscal year ended December 31, 2004

OR

o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES AND EXCHANGE ACT OF 1934

For the transition period from            to

Commission File Number 1-12193

ARDEN REALTY, INC.

11601 Wilshire Boulevard, 4th Floor
Los Angeles, California 90025-1740
(Address and zip code of principal executive offices)

Registrant’s telephone number, including area code: (310) 966-2600

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by checkmark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained to the best of the Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K, or any amendment to this Form 10-K. þ

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Act). Yes þ No o

The aggregate market value of the shares of common stock held by non-affiliates was approximately $1.9 billion based on the closing price on the New York Stock Exchange for such shares on June 30, 2004.

The number of the Registrant’s shares of common stock outstanding was 66,364,703 as of March 10, 2005.

DOCUMENTS INCORPORATED BY REFERENCE

Part III of this report incorporates information by reference from the definitive Proxy Statement for the 2005 Annual Meeting of Stockholders.

Table of Contents

EXPLANATORY NOTE

     This amendment to the Form 10-K of Arden Realty, Inc. is filed to correct the certification of the Chief Executive Officer under Rule 13a-14(a) or Rule 15d-14(a), filed as exhibit 31.1, and the certifications of the Chief Financial Officer and certain other executive officers under Rule 13a-14(a) or Rule 15d-14(a), filed as exhibit 31.2. The exhibits 31.1 and 31.2 originally filed inadvertently omitted reference to the company’s internal control over financial reporting.

PART IV

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K

(c) Exhibits

SIGNATURES

     Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized on April 14, 2005.

     Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.