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