Cover Page - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Dec. 10, 2021	Mar. 31, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	1-5103
Entity Registrant Name	BARNWELL INDUSTRIES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	72-0496921
Entity Address, Address Line One	1100 Alakea Street
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Honolulu
Entity Address, State or Province	HI
Entity Address, Postal Zip Code	96813-2840
City Area Code	808
Local Phone Number	531-8400
Title of 12(b) Security	Common Stock, $0.50 par value
Trading Symbol	BRN
Security Exchange Name	NYSEAMER
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
Entity Shell Company	false
Entity Public Float			$ 9,903
Entity Common Stock, Shares Outstanding		9,445,625
Documents Incorporated by Reference	Proxy statement, to be forwarded to stockholders on or about January 14, 2022, is incorporated by reference in Part III hereof.
Entity Central Index Key	0000010048
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30