Main Street Capital CORP

Board of Directors and Stockholders

Opinion on the financial statements

We have audited the accompanying consolidated balance sheets of Main Street Capital Corporation (a Maryland corporation) and subsidiaries (the “Company”), including the consolidated schedules of investments, as of December 31, 2025 and 2024, the related consolidated statements of operations, changes in net assets, and cash flows for each of the three years in the period ended December 31, 2025 and the related notes and financial statement schedule included under Item 15(2) (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (“PCAOB”), the Company’s internal control over financial reporting as of December 31, 2025, based on criteria established in the 2013 Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (“COSO”), and our report dated February 27, 2026 expressed an unqualified opinion.

Basis for opinion

These consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s consolidated financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our procedures included verification by confirmation of securities as of December 31, 2025 and 2024, by correspondence with the portfolio companies, agent banks and custodians, or by other appropriate auditing procedures where replies were not received. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical audit matter

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Fair Value of Level 3 Investments

As described further in Note C to the financial statements, the Company’s investments recorded at fair value, categorized as Level 3 investments within the fair value hierarchy, totaled $5,496,705 thousand at December 31, 2025. Approximately 97% of these investments have no readily available market values and are measured using significant unobservable inputs and assumptions, and generally use valuation techniques such as the income and market approach. The significant unobservable inputs disclosed by management include, among others, weighted-average cost of capital (“WACC”) inputs and market multiples for equity investments, and risk adjusted discount rates, and percentage of expected principal recovery for debt investments. Changes in these assumptions could have a significant impact on the determination of fair value. As such, we identified fair value of Level 3 investments measured using significant unobservable inputs and assumptions as a critical audit matter.

The principal consideration for our determination that the fair value of Level 3 investments measured using significant unobservable inputs and assumptions is a critical audit matter is management’s judgement used in identifying and evaluating significant unobservable inputs which result in estimation uncertainty for the fair value of Level 3 investments. Auditing these investments requires a high degree of subjective auditor judgment, including use of valuation professionals with specialized skills and knowledge, to evaluate the reasonableness of unobservable inputs and assumptions.

Our audit procedures related to the fair value of Level 3 investments measured using significant unobservable inputs and assumptions included the following, among others:

•We tested the design and operating effectiveness of management’s review controls relating to the Level 3 fair value measurement of investments. This included identifying and evaluating significant assumptions used in the estimation of fair value, such as the relevance, adequacy and appropriateness of these significant assumptions and valuation methods used to determine investment fair value as of the reporting date.

•With the assistance of internal valuation specialists, we tested management’s process for developing Level 3 investment fair values. For a selection of investments, we assessed the appropriateness of the methods and significant assumptions used in developing the estimate. The significant assumptions tested by us included, but were not limited to, the following:

•enterprise values,

•WACC,

•discount rates,

•forecasted cash flows and long-term growth rates,

•discount for lack of marketability,

•market multiples,

•weighting between valuation techniques,

•risk adjusted discount factor,

•market debt yields, or

•percentage of expected principal recovery

/s/GRANT THORNTON LLP

We have served as the Company’s auditor since 2007.

Dallas, Texas

February 27, 2026

Board of Directors and Stockholders

Opinion on internal control over financial reporting

We have audited the internal control over financial reporting of Main Street Capital Corporation (a Maryland corporation) and subsidiaries (the “Company”) as of December 31, 2025, based on criteria established in the 2013 Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (“COSO”). In our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in the 2013 Internal Control—Integrated Framework issued by COSO.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (“PCAOB”), the consolidated financial statements of the Company as of and for the year ended December 31, 2025, and our report dated February 27, 2026 expressed an unqualified opinion on those financial statements.

Basis for opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and limitations of internal control over financial reporting

A company’s 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 generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. 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.

/s/ GRANT THORNTON LLP

Dallas, Texas

February 27, 2026