Document And Entity Information - shares	6 Months Ended
	Mar. 31, 2024	May 02, 2024
Document And Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	1-34155
Entity Registrant Name	First Savings Financial Group, Inc.
Entity Incorporation, State or Country Code	IN
Entity Tax Identification Number	37-1567871
Entity Address, Address Line One	702 North Shore Drive
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Jeffersonville
Entity Address, State or Province	IN
Entity Address, Postal Zip Code	47130
City Area Code	812
Local Phone Number	283-0724
Title of 12(b) Security	Common stock, $0.01 par value per share
Trading Symbol	FSFG
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,883,160
Entity Central Index Key	0001435508
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false