Executive Change

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K/A (Amendment No. 1) CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 9, 2018 (January 3, 2018) Westamerica Bancorporation (Exact name of registrant as specified in its charter) California 001-09383 94-2156203 (State or other jurisdiction of incorporation) (Commission File No.) (IRS Employer Identification Number) 1108 Fifth Avenue San Rafael, California 94901 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: (707) 863-6000 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 (see General Instruction A.2. below): ☐ 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)) Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2). 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. ☐ EXPLANATORY NOTE This Form 8-K/A is being filed as an amendment (“Amendment No. 1”) to the Current Report on Form 8-K (“Original Report”) filed with the Securities and Exchange Commission under Item 5.02 on January 3, 2018. This Amendment No. 1 is being filed to update the effective retirement date of Mr. David L. Robinson. Section 5 – Corporate Governance and Management Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers (b) Departure of Banking Division Manager Effective January 31, 2018, David L. Robinson will retire from Westamerica Bank, Westamerica Bancorporation’s wholly-owned bank subsidiary. Mr. Robinson had served as Westamerica Bank’s Banking Division Manager since 2007. 2 SIGNATURES 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. WESTAMERICA BANCORPORATION (Registrant) Date: January 9, 2018 By: /s/ John “Robert” Thorson John “Robert” Thorson Senior Vice President and Chief Financial Officer