Note 6 - Investments in Joint Ventures - Condensed Income Statement of EXCOR and All Other Joint Ventures (Details) - USD ($)	3 Months Ended
	Nov. 30, 2023	Nov. 30, 2022
Net sales	$ 20,181,675	$ 19,952,766
Gross profit	7,334,274	6,353,124
Net income	895,521	502,242
Northern Technologies International Corporation’s share of equity in income of joint ventures	1,102,241	1,189,404
EXCOR and All Other Joint Venturs [Member]
Net income	2,204,482	2,646,908
Northern Technologies International Corporation’s share of equity in income of joint ventures	1,102,241	1,189,400
Northern Technologies International Corporation’s dividends received from joint ventures	371,104	3,042,688
EXCOR [Member]
Net income	1,026,907	1,742,287
Northern Technologies International Corporation’s share of equity in income of joint ventures	513,453	871,144
Northern Technologies International Corporation’s dividends received from joint ventures	0	2,459,500
All Other [Member]
Net income	1,177,575	904,621
Northern Technologies International Corporation’s share of equity in income of joint ventures	588,788	318,260
Northern Technologies International Corporation’s dividends received from joint ventures	371,104	583,188
EXCOR and All Other Joint Venturs [Member]
Net sales	23,560,661	24,730,289
Gross profit	10,103,800	9,693,568
EXCOR [Member]
Net sales	8,420,960	10,145,921
Gross profit	4,375,075	4,720,042
All Other [Member]
Net sales	15,139,701	14,584,368
Gross profit	$ 5,728,725	$ 4,973,526