UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

WESTERN ALLIANCE BANCORPORATION

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

957638 10 9

(CUSIP Number)

Western Alliance Bancorporation

2700 West Sahara Avenue

Las Vegas, NV 89102

Phone: (702) 248-4200

Attention: Corporate Secretary

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

October 12, 2005

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13-1(e), 13d-(f) or 13d-1(g), check the following box.  ¨

Note:  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Item 1. Security and Issuer

This Statement on Schedule 13D (this “Statement”) relates to shares of the common stock, $0.0001 par value per share, of Western Alliance Bancorporation, a Nevada corporation (the “Company”), whose principal executive offices are located at 2700 West Sahara Avenue, Las Vegas, NV 89102.

Item 2. Identity and Background

This Statement is filed on behalf of Marianne Boyd Johnson, whose business address is c/o Western Alliance Bancorporation, Attn: Corporate Secretary, 2700 West Sahara Avenue, Las Vegas, NV 89102.

Ms. Johnson is presently employed as Senior Vice President and serves as Vice Chairman of the Board of Directors of Boyd Gaming Corporation, a diversified owner of gaming entertainment properties whose principal executive offices are located at 2950 Industrial Road, Las Vegas, NV 89109. Ms. Johnson has also served as a member of the Company’s board of directors since it was established in 1995. Ms. Johnson has not, during the last five years, been convicted in a criminal proceeding or been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction which resulted in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violations with respect to such laws. Ms. Johnson is a U.S. citizen.

Item 3. Source and Amount of Funds or Other Consideration

The information provided in Item 4 hereof is incorporated herein by reference.

Item 4. Purpose of Transaction

On October 12, 2005, William S. Boyd (Ms. Johnson’s father) resigned as trustee of the Boyd-05 Grantor Retained Annuity Trust #1, the Boyd-05 Grantor Retained Annuity Trust #2 and the Boyd-05 Grantor Retained Annuity Trust #3 (collectively, the “GRATs”), each of which was established by Mr. Boyd. The GRATs collectively hold 3,988,847 shares of the Company’s common stock. Pursuant to the terms of each of the GRATs, Ms. Johnson succeeded Mr. Boyd as trustee upon his resignation.

The change in trustees under the GRATs was effected for estate planning purposes. No pecuniary interest in any of the Company’s securities was transferred as a result of Ms. Johnson’s becoming trustee under the GRATs, and no funds or other consideration was paid in connection therewith.

Ms. Johnson will review from time to time various factors relevant to her beneficial ownership of the Company’s securities, including trading prices for the Company’s common stock and conditions in capital markets generally, developments in the Company’s business and financial condition, results of operations and prospects, and other factors and, based thereon may, from time to time, dispose of some or all of the Company’s common stock that she beneficially holds, or acquire additional securities of the Company, in privately negotiated transactions, market sales or purchases, or otherwise. Ms. Johnson has in the past acquired, and may in the future acquire, stock options or other rights to purchase securities of the Company in the ordinary course of business in connection with her service on the Board of Directors of the Company.

Other than as set forth above and in her capacity as a director of the Company, Ms. Johnson has no present plans or proposals that relate to or would result in any of the actions described in Items 4(a) through (j) of Schedule 13D.

Item 5. Interest in Securities of the Issuer

(a), (b) The information set forth on the cover page of this Schedule 13D is incorporated herein by reference. Ms. Johnson holds dispositive and voting power over an aggregate of 4,607,931 shares of the Company’s common stock, consisting of 4,400 shares subject to stock options that are exercisable within 60 days of the date hereof, 3,988,847 shares held as trustee of the GRATs, 9,638 shares held as trustee of The William R. Boyd and Myong Boyd Children’s Trust, 290,712 shares held as trustee of The Marianne E. Boyd Trust, dated March 7, 1989, 71,910 shares held directly by Ms. Johnson, and 242,424 shares held by BG-05 Limited Partnership (through The Marianne E. Boyd Trust, dated March 7, 1989, as general partner thereof). Ms. Johnson expressly disclaims beneficial ownership in any securities of the Company except for those securities that are owned directly by her or to the extent of her pecuniary interest in a trust or other entity which owns such securities.

(c) The information included in Item 1 through Item 4 hereof is incorporated herein by reference. No other transactions in the Company’s common stock were effected during the 60 days prior to the date hereof by Ms. Johnson.

(d) Not applicable.

(e) Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Not applicable.

Item 7. Material to Be Filed as Exhibits

Not applicable.

Signature

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this Statement is true, complete and correct.

Date: October 21, 2005