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Date of Report (Date of earliest event reported):  November 19, 2025

(Exact name of registrant as specified in its charter)

One E. Washington Street, Phoenix, Arizona  85004

 (Address of principal executive offices)               (Zip Code)

(602) 389-3500

(Registrant's telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

On November 19, 2025, Western Alliance Bank (the “Bank”), a state member bank organized under the laws of the State of Arizona and the banking subsidiary of Western Alliance Bancorporation, a Delaware corporation (the “Company”), announced that it successfully priced $400,000,000 aggregate principal amount of 6.537% Fixed Rate Reset Subordinated Notes due 2035 (the “Notes”) in a transaction exempt from registration under Section 3(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). The offering is expected to settle on November 24, 2025, subject to customary closing conditions. The Bank intends to use the net proceeds from the offering for general corporate purposes, which may include providing capital to support its growth and the repayment, redemption or repurchase of existing securities. The Notes are intended to qualify as Tier 2 capital for bank regulatory purposes. The Notes are obligations solely of the Bank and are neither obligations of, nor guaranteed by, the Company or any of the Bank’s affiliates.

The information in this Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that Section, nor shall it be deemed subject to the requirements of amended Item 10 of Regulation S-K, nor shall it be deemed incorporated by reference into any filing of the Company under the Securities Act or the Exchange Act, whether made before or after the date hereof, regardless of any general incorporation language in such filing. The furnishing of this information hereby shall not be deemed an admission as to the materiality of any such information.

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.