Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2025	Nov. 18, 2025	Feb. 28, 2025
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Aug. 31, 2025
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 88.8
Entity Common Stock, Shares Outstanding (in shares)		9,480,689
Auditor Firm ID	23
Auditor Name	Baker Tilly US, LLP
Auditor Location	Minneapolis, Minnesota
Entity Central Index Key	0000875582
Current Fiscal Year End Date	--08-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Amendment Flag	false