Document And Entity Information - shares
 9 Months Ended
May 31, 2022
Jul. 08, 2022
Document Information [Line Items]    
Entity Central Index Key 0000875582  
Entity Registrant Name Northern Technologies International Corporation  
Amendment Flag false  
Current Fiscal Year End Date --08-31  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2022  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date May 31, 2022  
Document Transition Report false  
Entity File Number 001-11038  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 41-0857886  
Entity Address, Address Line One 4201 Woodland Road P.O. Box 69  
Entity Address, City or Town Circle Pines  
Entity Address, State or Province MN  
Entity Address, Postal Zip Code 55014  
City Area Code 763  
Local Phone Number 225-6600  
Title of 12(b) Security Common stock, par value $0.02 per share  
Trading Symbol NTIC  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   9,232,483