Exhibit 4

Exhibit 4.5

MAIN STREET CAPITAL CORPORATION

2022 NON-EMPLOYEE DIRECTOR RESTRICTED STOCK PLAN

1. PURPOSE OF THIS PLAN

The purpose of this Restricted Stock Plan (this “Plan”) is to advance the interests of Main Street Capital Corporation (the “Company”) by providing to members of the Company’s Board of Directors who are not employees of the Company (“Non-Employee Directors”) additional incentives, to the extent permitted by law, to exert their best efforts on behalf of the Company, and to provide a means to attract and retain persons of outstanding ability to the service of the Company. It is recognized that the Company’s efforts to attract or retain these individuals will be facilitated with this additional form of compensation.

2. ADMINISTRATION

This Plan shall be administered by the Compensation Committee (the “Committee”) of the Company’s Board of Directors (“Board”), which is comprised solely of directors who are not interested persons of the Company within the meaning of Section 2(a)(19) of the Investment Company Act of 1940, as amended (the “Act”). The Committee shall interpret this Plan and, to the extent and in the manner contemplated herein, shall exercise the discretion reserved to it hereunder. The Committee may prescribe, amend and rescind rules and procedures relating to this Plan and make all other determinations necessary for its administration. The decision of the Committee on any interpretation of this Plan or administration hereof, if in compliance with the provisions of the Act and regulations promulgated thereunder, shall be final and binding with respect to the Company and the Non-Employee Directors.

3. SHARES SUBJECT TO THIS PLAN

The shares subject to this Plan shall be shares of the Company’s common stock, par value $0.01 per share (“Shares”). Subject to the provisions hereof concerning adjustment, the total number of shares that may be awarded as restricted shares under this Plan shall not exceed 300,000 Shares. Any Shares that were granted pursuant to an award of restricted stock under this Plan but that are forfeited pursuant to the terms of this Plan or an award agreement shall again be available under this Plan. Shares used for tax withholding shall not again be available under this Plan. Shares may be made available from authorized, un-issued or reacquired stock or partly from each.

4. AWARDS

(A) Non-Employee Directors. Non-Employee Directors will each receive a grant of shares of restricted stock at or about the beginning of each one-year term of service on the Board, for which forfeiture restrictions will lapse at the end of that term; provided that the Board may provide in any award agreement, or may determine in any individual case, that restrictions or forfeiture conditions relating to restricted stock will be waived in whole or in part in the event of terminations resulting from any cause, and the Board may in other cases waive in whole or in part the forfeiture of restricted stock. The number of shares of restricted stock granted to each Non-Employee

Director each year will be the equivalent of $30,000 worth of shares based on the market value at the close of the exchange on the date of grant.

(B) Award Agreements. All restricted stock granted under this Plan will be evidenced by an agreement. The agreement documenting the award of any restricted stock granted pursuant to this Plan shall contain such terms and conditions as the Committee shall deem advisable, including but not limited to the lapsing of forfeiture restrictions. Agreements evidencing awards made to different participants or at different times need not contain similar provisions. In the case of any discrepancy between the terms of this Plan and the terms of any award agreement, this Plan provisions shall control.

(C) Stockholder Rights. Holders of restricted stock shall have all the rights of a holder upon issuance of the restricted stock award including, without limitation, voting rights and the right to receive dividends.

5. LIMITATIONS ON RESTRICTED STOCK AWARDS

Grants of restricted stock awards shall be subject to the following limitations:

(A) The combined maximum amount of restricted stock that may be issued under this Plan and the Company’s 2022 Equity Incentive Plan (together, the “Plans”) and any other compensation plans of the Company is 10% of the outstanding shares of the Company on the effective date of the Plans plus 10% of the number of shares of the Company issued or delivered by the Company (other than pursuant to compensation plans) during the term of the Plans. No one person shall be granted restricted stock relating to more than 25% of the shares available for issuance under this Plan.

(B) The amount of voting securities that would result from the exercise of all of the Company’s outstanding warrants, options, and rights, together with any restricted stock issued pursuant to the Plans and any other compensation plan of the Company at the time of issuance shall not exceed 25% of the outstanding voting securities of the Company, provided, however, that if the amount of voting securities that would result from the exercise of all of the Company’s outstanding warrants, options, and rights issued to the Company’s directors, officers, and employees, together with any restricted stock issued pursuant to the Plans and any other compensation plan of the Company, would exceed 15% of the outstanding voting securities of the Company, then the total amount of voting securities that would result from the exercise of all outstanding warrants, options, and rights, together with any restricted stock issued pursuant to the Plans and any other compensation plan of the Company at the time of issuance shall not exceed 20% of the outstanding voting securities of the Company.

6. TRANSFERABILITY OF RESTRICTED STOCK

While subject to forfeiture provisions, restricted stock shall not be transferable other than to the spouse or lineal descendants (including adopted children) of the participant, any trust for the benefit of the participant or the benefit of the spouse or lineal descendants (including adopted children) of the participant, or the guardian or conservator of the participant (“Permitted Transferees”).

7. EFFECT OF CHANGE IN STOCK SUBJECT TO THIS PLAN

(A)Capitalization Adjustments. In the event of a stock dividend, stock split or combination of shares (including a reverse stock split), recapitalization or other change in the Company’s capital structure, the Board will make appropriate adjustments to the maximum number of shares that may be delivered under this Plan, to the maximum per-participant share limit, and will also make appropriate adjustments to the number and kind of shares of stock or securities subject to awards then outstanding or subsequently granted and any other provision of awards affected by such change. To the extent consistent with continued exclusion from or compliance with Section 409A of the Internal Revenue Code of 1986, as amended and in effect, or any successor statute as from time to time in effect, and other applicable law, the Board may also make adjustments of the type described in the preceding sentence to take into account distributions to stockholders other than those provided for in such sentence, or any other event, if the Board determines that adjustments are appropriate to avoid distortion in the operation of this Plan and to preserve the value of awards granted hereunder.

(B)Change in Control. Except as otherwise provided in an award, in the event of a Change in Control (as defined below) in which there is an acquiring or surviving entity, the Board may provide for the assumption of some or all outstanding awards, or for the grant of new awards in substitution therefor, by the acquirer or survivor or an affiliate of the acquirer or survivor, in each case on such terms and subject to such conditions as the Board determines. In the absence of such an assumption or if there is no substitution, except as otherwise provided in the award, each award will become fully vested or exercisable prior to the Change in Control on a basis that gives the holder of the award a reasonable opportunity, as determined by the Board, to participate as a stockholder in the Change in Control following vesting or exercise, and the award will terminate upon consummation of the Change in Control.

A “Change in Control” means an event set forth in any one of the following paragraphs:

(i)any “person” or group (as defined in Section 3(a)(9) of the Securities Exchange Act of 1934 (as amended, and including the rules and regulations promulgated thereunder, the “Exchange Act”), and as modified in Section 13(d) and 14(d) of the Exchange Act), together with their affiliates and associates (both as defined in Rule 12b-2 under the Exchange Act) other than (i) the Company or any of its subsidiaries, (ii) any employee benefit plan of the Company or any of its subsidiaries, or the trustee or other fiduciary holding securities under any such employee benefit plan, (iii) a company owned, directly or indirectly, by stockholders of the Company in substantially the same proportions as their ownership of the Company or (iv) an underwriter temporarily holding securities pursuant to an offering of such securities by the Company, becomes the “beneficial owner” (as defined in Rule 13d-3 of the Exchange Act), directly or indirectly, of more than 30% of combined voting power of the voting securities of the Company then outstanding; or

(ii)individuals who, as of the effective date of this Plan, constitute the Board (the “Incumbent Board”) cease for any reason to constitute at least a majority of the Board; provided, however, that for purposes of this definition of Change in Control, any individual becoming a director subsequent to the effective date of this Plan whose

appointment or nomination for election to the Board was approved by a vote of at least a majority of the directors then comprising the Incumbent Board shall be considered as though such individual were a member of the Incumbent Board, but excluding, for this purpose, any such individual whose initial assumption of office occurs as a result of an election contest with respect to the election or removal of directors or other solicitation of proxies or consents by or on behalf of a person other than the Board; or

(iii)the consummation of any merger, reorganization, business combination or consolidation of the Company or one of its subsidiaries (a “Business Combination”) with or into any other entity, other than a merger, reorganization, business combination or consolidation a result of which (or immediately after which) the holders of the voting securities of the Company outstanding immediately prior thereto holding securities would represent immediately after such merger, reorganization, business combination or consolidation more than a majority of the combined voting power of the voting securities of the Company or the surviving entity or the parent of such surviving entity; or

(iv)the consummation of a sale or disposition by the Company of all or substantially all of the Company’s assets, other than a sale or disposition if the holders of the voting securities of the Company outstanding immediately prior thereto hold securities immediately thereafter which represent more than a majority of the combined voting power of the voting securities of the acquirer, or parent of the acquirer, of such assets; or

(v)the stockholders of the Company approve a plan of complete liquidation or dissolution of the Company.

Notwithstanding the foregoing, a “Change in Control” shall not be deemed to have occurred by virtue of the consummation of any transaction or series of integrated transactions immediately following which the record holders of the stock of the Company immediately prior to such transaction or series of transactions continue to have substantially the same proportionate ownership in an entity which owns all or substantially all of the assets of the Company immediately following such transaction or series of transactions.

8. MISCELLANEOUS PROVISIONS

(A) The Committee is authorized to take appropriate steps to ensure that neither the grant of nor the lapsing of the forfeiture restrictions on awards under this Plan would have an effect contrary to the interests of the Company’s stockholders. This authority includes the authority to prevent or limit the granting of additional awards under this Plan.

(B) The granting of any award under this Plan shall not impose upon the Company any obligation to appoint or to continue to appoint as a director or employee any participant, and the right of the Company and its subsidiaries to terminate the employment of any employee, or service of any director, shall not be diminished or affected by reason of the fact that an award has been made under this Plan to such participant.

(C) The Company may make such provisions as it deems appropriate to withhold any taxes the Company determines it is required to withhold with respect to any award.

(D) This Plan and all awards and actions taken hereunder shall be governed by the laws of the state of Texas, without regard to the choice of law principles of any jurisdiction.

9. AMENDMENT AND TERMINATION

(A) The Board may modify, revise or terminate this Plan at any time and from time to time, subject to applicable requirements in (a) the Company’s articles of incorporation or by-laws and (b) applicable law and orders. The Board shall seek stockholder approval of any action modifying a provision of this Plan where it is determined that such stockholder approval is appropriate under the provisions of (a) applicable law or orders, or (b) the Company’s articles of incorporation or by-laws.

(B) Unless sooner terminated, this Plan shall terminate on the day before the tenth (10th) anniversary of the date this Plan is approved by the stockholders of the Company. Notwithstanding the termination of this Plan, awards granted prior to termination of this Plan shall continue to be effective and shall be governed by this Plan.

10. EFFECTIVE DATE OF THIS PLAN

This Plan shall become effective upon the approval of this Plan by the shareholders of the Company.

Adopted: February 23, 2022; Effective: May 2, 2022