EX-32.(A) 4 iboc-20250630xex32da.htm EX-32.(A)

Exhibit 32(a)

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CERTIFICATION PURSUANT TO

18 U.S.C. 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

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In connection with the Quarterly Report of International Bancshares Corporation (the “Company”) on Form 10-Q for the period ended June 30, 2025, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Dennis E. Nixon, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

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| (1) | The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m(a) or 78o(d)), as applicable; and

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| (2) | The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

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​ | By: | /s/ Dennis E. Nixon
​ | ​ | Dennis E. Nixon
​ | ​ | President
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​ | Date: | August 7, 2025

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The foregoing certification is being furnished solely to accompany the Report pursuant to 18 U.S.C. 1350, and not being filed for purposes of Section 18 of the Securities Exchange Act, as amended, and is not to be incorporated by reference into any filing of the Company, whether on, before or after the date hereof, regardless of any general incorporation language in such filing.

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A signed original of this written statement required by Section 906 has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.