Exhibit 99.1 Winchester Bancorp, Inc. Announces Results for the Quarter Ended March 31, 2026 Investor Contact John A. Carroll President and Chief Executive Officer IR@WinchesterSavings.com (781) 729-2130 BALANCE SHEET Total assets were $1.06 billion at March 31, 2026, representing an increase of $107.7 million, or 11.3%, from June 30, 2025. 1 • Cash and cash equivalents were $54.0 million, reflecting a decrease of $1.3 million from June 30, 2025. • Net loans were $840.5 million, representing an increase of ...