Exhibit 32.1

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of National Mercantile Bancorp (the “Company”) on Form 10-QSB for the period ending September 30, 2006 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Scott A. Montgomery, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(1)  The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)  The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of and for the periods covered in the report.

/s/ SCOTT A. MONTGOMERY

Scott A. Montgomery

Chief Executive Officer

Date:  November 14, 2006

A signed original of this written statement required by Section 906, or other document authenticating, acknowledging, or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to National Mercantile Bancorp and will be retained by National Mercantile Bancorp and furnished to the Securities and Exchange Commission or its staff upon request.

The foregoing certification is being furnished to the Securities and Exchange Commission as an exhibit to the Form 10-QSB and shall not be considered filed as part of the Form 10-QSB.