UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant  ☒

Filed by a Party other than the Registrant  ☐

Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material under §240.14a-12

BankGuam Holding Company

(Name of registrant as specified in its charter)

(Name of person(s) filing proxy statement, if other than the registrant)

Payment of Filing Fee (Check the appropriate box):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

+ C 1234567890 000004 MMMMMM ENDORSEMENT_LINE SACKPACK MR A SAMPLE Online DESIGNATION (IF ANY) ADD 1 Go to www.envisionreports.com/BKGM or scan ADD 2 the QR code — login details are located in the ADD 3 shaded bar below. ADD 4 ADD 5 ADD 6 Votes submitted electronically must be received by 5:00 p.m., CHamoru Standard Time, on July 25, 2022. Shareholder Meeting Notice 1234 5678 9012 345 Important Notice Regarding the Availability of Proxy Materials for the BankGuam Holding Company Meeting to be Held on July 25, 2022 Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual shareholders’ meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy. The items to be voted on and location of the annual meeting are on the reverse side. Your vote is important! This communication presents only an overview of the more complete proxy materials that are available to you on the Internet or by mail. We encourage you to access and review all of the important information contained in the proxy materials before voting. The Proxy Card, Proxy Statement, Form 10K, Year in Review to shareholders are available at: www.envisionreports.com/BKGM Easy Online Access — View your proxy materials and vote. Step 1: Go to www.envisionreports.com/BKGM. Step 2: Click on Cast Your Vote or Request Materials. Step 3: Follow the instructions on the screen to log in. Step 4: Make your selections as instructed on each screen for your delivery preferences. Step 5: Vote your shares. When you go online, you can also help the environment by consenting to receive electronic delivery of future materials. Obtaining a Copy of the Proxy Materials – If you want to receive a paper or e-mail copy of these documents, you must request one. There is no charge to you for requesting a paper or e-mail copy. Please make your request for a paper or e-mail copy as instructed on the reverse side on or before July 1, 2022 to facilitate timely delivery. 2NOT COY + 03M1WF

Shareholder Meeting Notice BANKGUAM HOLDING COMPANY Annual Meeting of Shareholders will be held on July 25, 2022 at the Company’s Headquarters located at 111 W. Chalan Santo Papa, in Hagĺtńa, Territory of Guam 96910, at 7:00 P.M. CHamoru Standard Time. Proposals to be voted on at the meeting are listed below along with the Board of Directors’ recommendations. The Board of Directors recommends a vote FOR all the nominees listed on Proposal 1, and FOR Proposals 2 and 3. 1. Election of four Class II Directors for a term of three years. 2. To vote to approve an amendment to the Company’s Articles of Incorporation, whereby the Company will effect a 1-for-500 reverse stock split 3. To ratify the selection of Baker Tilly US, LLP as the Company’s independent registered public accounting firm for the year ending December 31, 2022 And to transact such other business as may properly come before the Annual Meeting and any adjournment or postponement thereof. PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must vote online, request a paper copy of the proxy materials to receive a proxy card, or attend the meeting. If you wish to attend and vote at the meeting, please bring this notice with you. At the meeting you will need to request a ballot to vote your shares. Here’s how to order a copy of the proxy materials and select delivery preferences: Current and future delivery requests can be submitted using the options below. If you request an email copy, you will receive an email with a link to the current meeting materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a copy of the proxy materials. — Internet – Go to www.envisionreports.com/BKGM. Click Cast Your Vote or Request Materials. — Phone – Call us free of charge at 1-866-641-4276. — Email – Send an email to investorvote@computershare.com with “Proxy Materials BankGuam Holding Company” in the subject line. Include your full name and address, plus the number located in the shaded bar on the reverse side, and state that you want a paper copy of the meeting materials. To facilitate timely delivery, all requests for a paper copy of proxy materials must be received by July 1, 2022.