UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No.    )

BankFinancial Corporation

(Name of Issuer)

Common Stock, $0.01 par value

(Title of Class of Securities)

06643P104

(CUSIP Number)

Mr. John W. Palmer

PL Capital Advisors, LLC

750 Eleventh Street South

Suite 202

Naples, FL 34102

(239) 777-0187

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

- with copies to -

May 7, 2021

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐


Rule 13d-1(b)

☒


Rule 13d-1(c)

☐


Rule 13d-1(d)

Explanatory Note

The Reporting Persons (as defined below) were initially eligible to report their beneficial ownership on a Schedule
13G with respect to the securities of the Issuer (as defined below), pursuant to Rule 13d-1(c) of the Securities Exchange Act of 1934, as amended (the “

Exchange Act

”), and subsequently held securities of the Issuer with a purpose or
effect of changing or influencing control of the Issuer, which required a filing on Schedule 13D.  The Schedule 13D was filed on February 14, 2013, and has subsequently been amended in compliance with Rule 13d-2 of the Exchange Act (the “

Schedule 13D

”).  As of May 7, 2021, the Reporting Persons no longer hold securities of
the Issuer with a purpose or effect of changing or influencing control of the Issuer, or in connection with or as a participant in any transaction having that purpose or effect.  Accordingly, the Reporting Persons are converting the Schedule 13D,
with the last amendment to the Schedule 13D having been made on May 14, 2020, to a Schedule 13G pursuant to Rule 13d-1(h) of the Exchange Act.  This Schedule 13G reflects the ownership of the Reporting Persons in the Issuer as of May 7, 2021.

Item 1(a).

Name of Issuer :

BankFinancial Corporation

Item 1(b).

Address of Issuer’s Principal Executive Offices :

60 North Frontage Road, Burr Ridge, IL 60527

This Schedule 13G is being filed jointly by (1) PL Capital Advisors, LLC, a Delaware limited
liability company and SEC registered investment adviser under the Investment Advisers Act of 1940 (“

PL Capital Advisors

”); (2) Richard J. Lashley, a managing
member of PL Capital Advisors; and (3) John W. Palmer, a managing member of PL Capital Advisors (collectively, the “

Reporting Persons

”).

The business address of PL Capital Advisors, LLC, Mr. Palmer and Mr. Lashley is:  c/o PL
Capital, 750 Eleventh Street South, Suite 202, Naples, FL 34102.

All of the individuals who are members of the PL Capital Advisors are citizens of the United
States.

Common Stock

06643P104

N/A

Item 4.

Ownership :

The following list sets forth the aggregate number and percentage (based on 14,583,284 shares
of Common Stock outstanding as of April 28, 2021, as reported in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on April 30, 2021) of outstanding shares of Common Stock owned beneficially by each
reporting person named in Item 2(a):

N/A

Item 6.

Ownership of More than Five Percent on Behalf of Another Person :

PL Capital Advisors manages the assets of various advisory clients who have the right to
receive dividends from, or the proceeds from the sale of, the securities described herein.

N/A

Item 8.

Identification and Classification of Members of the Group :

See Item 2(a) above.

N/A

Item 10.

Certification :

By signing below I certify that, to the best of my knowledge and belief, the securities referred
to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction
having that purpose or effect, other than activities solely in connection with a nomination under Rule 14a-11.

List of Exhibits

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, we certify that the information set forth in
this statement is true, complete and correct.

Date:  May 7, 2021.

Signature Page

EXHIBIT 99.1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to
the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto) with respect to the common stock, $0.01 par value, of BankFinancial Corporation, and further agree that this Joint Filing Agreement
shall be included as an exhibit to such joint filing.

The undersigned agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13G
and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other
party, unless such party knows or has reason to believe that such information is inaccurate.

This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each
counterpart were upon the same instrument.

Dated:  May 7, 2021