Mayville Engineering Company, Inc.

Evaluation of Disclosure Controls and Procedures

We maintain disclosure controls and procedures that are designed to provide reasonable assurance that information required to be disclosed in the reports we file or submit under the Securities Exchange Act of 1934, as amended (the Exchange Act), is recorded, processed, summarized and reported within the time periods specified in the rules and forms of the SEC, and that such information is accumulated and communicated to our management, including our Chief Executive Officer and Chief Financial Officer, to allow for timely decisions regarding required disclosure. In designing disclosure controls and procedures, our management necessarily was required to apply its judgment in evaluating the cost-benefit relationship of possible disclosure controls and procedures. The design of any disclosure controls and procedures also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving the desired objectives.

As of December 31, 2025, we carried out an evaluation, under the supervision and with the participation of our Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act). Based on this evaluation, our Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures were effective as of December 31, 2025. Management believes the consolidated financial statements included in this Annual Report on Form 10-K fairly present, in all material respects, our financial position, results of operations and cash flows as of the dates presented, and for the periods ended on such dates, in conformity with accounting principles generally accepted in the United States of America (GAAP).

Management’s Report on Internal Control Over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Rules 13a-15(f) and 15d-15(f) of the Exchange Act. Internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with GAAP. Our internal control over financial reporting includes those policies and procedures that: (i) pertain to the maintenance of records that in reasonable detail accurately and fairly reflect the transactions and dispositions of our assets, (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with GAAP, and that our receipts and expenditures are being made only in accordance with authorizations of our management and directors, and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of our assets that could have a material effect on our financial statements.

Our management, under the supervision of our Chief Executive Officer and Chief Financial Officer, evaluated the effectiveness of our internal control over financial reporting as of the end of the most recent fiscal year, December 31, 2025, utilizing the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission ("COSO") in theInternal Control-Integrated Framework (2013). Based on this evaluation, our management concluded that we maintained effective internal control over financial reporting as of December 31, 2025. In accordance with guidance issued by the Securities and Exchange Commission staff, companies are permitted to exclude acquisitions from their assessment of internal control over financial reporting for the first fiscal year in which the acquisition occurred. Accordingly, in conducting this assessment, our management excluded Accu-Fab, Inc., which was acquired on July 1, 2025, and whose financial statements constitute 2% and 3% of net and total assets (excluding acquired goodwill and intangibles which were included in management’s assessment of internal control over financial reporting as of December 31, 2025), respectively, and 7% of net sales of the consolidated financial statement amounts as of and for the year ended December 31, 2025.

Deloitte & Touche LLP, our independent registered public accounting firm, has issued an attestation report on the effectiveness of our internal control over financial reporting as of December 31, 2025. Consistent with management, Deloitte & Touch LLP’s internal control over financial reporting opinion excluded Accu-Fab, Inc.

Previously Disclosed Material Weakness

In fiscal year 2024, management identified deficiencies in the design and operating effectiveness of internal control over financial reporting related to the review and approval of journal entries that constituted a material weakness. During fiscal year 2025, management under the oversight of the Audit Committee implemented measures to remediate the material weakness, including:

We have completed the design and operating effectiveness testing of the enhanced controls. Based on this testing, our Chief Executive Officer and Chief Financial Officer concluded that the previously disclosed material weakness was remediated as of December 31, 2025.

Changes in Internal Control Over Financial Reporting

Other than the acquisition of Accu-Fab, which has been excluded from management’s assessment as described above, and the remediation of the previously identified material weakness, there were no changes in internal control over financial reporting during the three months ended December 31, 2025 that materially affected, or are reasonably likely to materially affect, our internal controls over financial reporting.