Document And Entity Information - shares	6 Months Ended
	Feb. 28, 2023	Apr. 11, 2023
Document Information [Line Items]
Document Type	10-Q/A
Document Quarterly Report	true
Document Period End Date	Feb. 28, 2023
Document Transition Report	false
Entity File Number	001-11038
Entity Registrant Name	NORTHERN TECHNOLOGIES INTERNATIONAL CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	41-0857886
Entity Address, Address Line One	4201 Woodland Road
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 (in shares)		9,366,358
Amendment Description	This Amendment No. 1 to Quarterly Report on Form 10-Q/A (Amended Report) amends and restates certain information included in the Quarterly Report on Form 10-Q for the three and six months ended February 28, 2023 filed by Northern Technologies International Corporation (the Company) with the Securities and Exchange Commission (SEC) on April 13, 2023 (the Original Report).
Entity Central Index Key	0000875582
Current Fiscal Year End Date	--08-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	true