UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of ~~the~~Report ~~Securities~~(Date ~~Exchange~~of ~~Act~~earliest ofevent ~~1934~~reported): July 31, 2025

Date of Report (Date of earliest event reported): July 24, 2025

Avidia Bancorp, Inc.

(Exact Name of Registrant as Specified in its Charter)

Maryland	~~333~~001-~~285815~~42775	33-4239888
(State or Other Jurisdictionof Incorporation)	(CommissionFile No.)	(I.R.S. EmployerIdentification No.)
(State or Other Jurisdiction of Incorporation)	(Commission File No.)	(I.R.S. Employer Identification No.)
42 Main Street, Hudson, Massachusetts		~~01749~~	01749
(Address of Principal Executive Offices)		~~(Zip Code)~~	(Zip Code)

(800) 508-2265

(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))

☐ 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:

Title of Each Class TradingSymbol(s) Name of Each Exchangeon Which Registered

Common stock, $0.01 par value per share		AVBC		The New York Stock Exchange
Title of Each Class		Trading Symbol(s)		Name of Each Exchange on Which Registered

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

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. ☐

Item 8.01 Other Events.

On July 24 31, 2025, Avidia Bancorp, Inc., the ~~proposed~~ stock holding company of Avidia Bank, ~~issued~~closed ~~a press release to announce the expected closing date of~~ its initial public offering in connection with the mutual-to-stock conversion of Assabet Valley Bancorp, the former mutual holding company of Avidia Bank. For Afurther ~~copy~~information, ofreference is made to the press release is filed as an exhibit hereto and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

ExhibitNo.		Description
99.1		Press Release dated July 24, 2025
104		Cover Page Interactive Data File (Embedded within Inline XBRL document)

Exhibit No. Description

99.1

Press Release dated July 31, 2025

104

Cover Page Interactive Data File (Embedded within Inline XBRL document)

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.

	Avidia Bancorp, Inc.


Date: July 31, 2025	By: /s/ Jonathan Nelson Jonathan Nelson Chief Financial Officer

Avidia Bancorp, Inc.

Date: July 24, 2025

/s/ Robert D. Cozzone

Robert D. Cozzone

President and Chief Executive Officer

Filing Compare · Avidia Bancorp, Inc.