Cover
Jul. 08, 2021
Cover [Abstract]  
Document Type 8-K
Amendment Flag false
Document Period End Date Jul. 08, 2021
Entity File Number 001-11038
Entity Registrant Name NORTHERN TECHNOLOGIES INTERNATIONAL CORPORATION
Entity Central Index Key 0000875582
Entity Tax Identification Number 41-0857886
Entity Incorporation, State or Country Code DE
Entity Address, Address Line One 4201 Woodland RoadP.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
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Title of 12(b) Security Common stock, par value $0.02 per share
Trading Symbol NTIC
Security Exchange Name NASDAQ
Entity Emerging Growth Company false