NB Bancorp, Inc.

(a)Evaluation of Disclosure Controls and Procedures: An evaluation of the Company's disclosure controls and procedures (as defined in Section 13a-15(e) of the Securities Exchange Act of 1934 (the "Act")) was carried out as of December 31, 2025 under the supervision and with the participation of the Company's Chief Executive Officer, Chief Financial Officer and several other members of the Company's senior management as of the end of the period covered by this report. The Company's Chief Executive Officer and Chief Financial Officer concluded that based on their evaluation at December 31, 2025, the Company's disclosure controls and procedures were effective in ensuring that the information required to be disclosed by the Company in the reports it files or submits under the Act is (i) accumulated and communicated to the Company's management (including the Chief Executive Officer and Chief Financial Officer) in a timely manner to allow timely decisions regarding required disclosure, specified in the SEC’s rules and forms, and (ii) recorded, processed, summarized and reported within the time periods specified in the SEC's rules and forms.

(b)Report of Management on Internal Control over Financial Reporting: The management of the Company is responsible for establishing and maintaining adequate internal control over financial reporting.

The internal control process has been designed under our supervision to provide reasonable assurance regarding the reliability of financial reporting and the preparation of the Company's consolidated financial statements for external reporting purposes in accordance with accounting principles generally accepted in the United States of America.

Management conducted an assessment of the effectiveness of the Company's internal control over financial reporting as of December 31, 2025, utilizing the framework established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). Based on this assessment, management has determined that the Company's internal control over financial reporting as of December 31, 2025 is effective.

Our internal control over financial reporting includes policies and procedures that pertain to the maintenance of records that accurately and fairly reflect, in reasonable detail, transactions and dispositions of assets; and provide reasonable assurances that: (1) transactions are recorded as necessary to permit preparation of financial statements in accordance with accounting principles generally accepted in the United States; (2) receipts and expenditures are being made only in accordance with authorizations of management and the directors of the Company; and (3) unauthorized acquisition, use, or disposition of the Company's assets that could have a material effect on the Company's consolidated financial statements are prevented or timely detected.

All internal control systems, no matter how well designed, have inherent limitations. Therefore, even those systems determined to be effective can provide only reasonable assurance with respect to financial statement preparation and presentation.

Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

This Form 10-K does not include an attestation report of the Company's independent registered public accounting firm regarding internal control over financial reporting because the Company is an emerging growth company. Management's report was not subject to attestation by the Company's independent registered public accounting firm pursuant to rules of the SEC that permit the Company to provide only management's report in this Form 10-K.

(c)Changes in Internal Controls: There have been no changes in the Company's internal control over financial reporting during the quarter ended December 31, 2025 that have materially affected, or are reasonably likely to materially affect, the Company's internal control over financial reporting.