UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-42627 WINCHESTER BANCORP, INC. (Exact name of Registrant as specified in its Charter) (State or other jurisdiction of incorporation or or ...

Exhibit 99.1 Announces Results for the Year Ended June 30, 2025 Investor Contact John A. Carroll President and Chief Executive Officer IR@WinchesterSavings.com (781) 729-2130 WINCHESTER, MA, July 30, 2025 - Winchester Bancorp, Inc. (NASDAQ-WSBK) (the "Company"), the holding company for Winchester Savings Bank (the "Bank"), today announced its 2025 financial results. As described in the prospectus for its initial public offering ("IPO"), concurrent with the completion of its reorganization and stock offering ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from __________ to __________ Commission File Number: 333-283752 WINCHESTER BANCORP, INC. (Exact Name of Registrant as Specified in its Charter) | Maryland | 33-3361 ...

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 Report (Date of earliest event reported): April 30, 2025 WINCHESTER BANCORP, INC. (Exact Name of Registrant as Specified in Charter) (State or Other Jurisdiction of Incorporation) Maryland 333-283752 33-3361275 (Commission File No.) (I.R.S. Employer ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended December 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from __________ to __________ Commission File Number: 333-283752 WINCHESTER BANCORP, INC. (Exact Name of Registrant as Specified in its Charter) | | Trading | | | ...