**Exhibit 31.1**

**CERTIFICATION PURSUANT TO SECTION 302(A) OF THE SARBANES-OXLEY ACT OF 2002**

| I, G.   Patrick Lynch, certify that: |
|--------------------------------------|
|                                 |   |   |
| 1.                                   | I have   reviewed this quarterly report on Form 10-QSB of Northern Technologies   International Corporation; |
|                                 |   |   |
| 2.                                   | Based on my   knowledge, this report does not contain any untrue statement of a material   fact or omit to state a material fact necessary to make the statements made,   in light of the circumstances under which such statements were made, not   misleading with respect to the period covered by this report; |
|                                 |   |   |
| 3.                                   | Based on my   knowledge, the financial statements, and other financial information included   in this report, fairly present in all material respects the financial   condition, results of operations and cash flows of the small business issuer   as of, and for, the periods presented in this report; |
|                                 |   |   |
| 4.                                   | The small   business issuer’s other certifying officers and I are responsible for   establishing and maintaining disclosure controls and procedures (as defined   in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the small business issuer   and have: |
|                                 |   |   |
|                                 |   | (a)          Designed   such disclosure controls and procedures, or caused such disclosure controls   and procedures to be designed under our supervision, to ensure that material   information relating to the small business issuer, including its consolidated   subsidiaries, is made known to us by others within those entities,   particularly during the period in which this report is being prepared; |
|                                 |   |   |
|                                 |   | (b)          Evaluated   the effectiveness of the small business issuer’s disclosure controls and   procedures and presented in this report our conclusions about the   effectiveness of the disclosure controls and procedures, as of the end of the   period covered by this report based on such evaluation; and |
|                                 |   |   |
|                                 |   | (c)          Disclosed in   this report any change in the small business issuer’s internal control over   financial reporting that occurred during the small business issuer’s fourth   quarter that has materially affected, or is reasonably likely to materially   affect, the small business issuer’s internal control over financial   reporting; and |
|                                 |   |   |
| 5.                                   | The small   business issuer’s other certifying officers and I have disclosed, based on   our most recent evaluation of internal controls over financial reporting, to   the small business issuer’s auditors and the audit committee of the small   business issuer’s board of directors (or persons performing the equivalent   function): |
|                                 |   |   |
|                                 |   | (a)          All   significant deficiencies and material weaknesses in the design or operation   of internal controls over financial reporting which are reasonably likely to   adversely affect the small business issuer’s ability to record, process,   summarize and report financial information; and |
|                                 |   |   |
|                                 |   | (b)          Any fraud,   whether or not material, that involves management or other employees who have   a significant role in the small business issuer’s internal controls over   financial reporting. |

 

| Date:  July 14, 2006 |   |                                       |
|---------------------------|--------|---------------------------------------|
|                      |   |                                       |
|                      |   | G. Patrick Lynch                      |
|                      |   | President and Chief Executive Officer |