v3.25.3

COVER - shares	6 Months Ended
COVER - shares	Sep. 30, 2025	Nov. 03, 2025
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2025
Document Transition Report	false
Entity File Number	814-00704
Entity Registrant Name	GLADSTONE INVESTMENT CORPORATION\DE
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-0423116
Entity Address, Address Line One	1521 WESTBRANCH DRIVE
Entity Address, Address Line Two	SUITE 100
Entity Address, City or Town	MCLEAN
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22102
City Area Code	703
Local Phone Number	287-5800
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		39,646,451
Entity Central Index Key	0001321741
Current Fiscal Year End Date	--03-31
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Amendment Flag	false
Common Stock, $0.001 par value per share
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	GAIN
Security Exchange Name	NASDAQ
5.00% Notes due 2026
Document Information [Line Items]
Title of 12(b) Security	5.00% Notes due 2026
Trading Symbol	GAINN
Security Exchange Name	NASDAQ
4.875% Notes due 2028
Document Information [Line Items]
Title of 12(b) Security	4.875% Notes due 2028
Trading Symbol	GAINZ
Security Exchange Name	NASDAQ
8.00% 2028 Notes
Document Information [Line Items]
Title of 12(b) Security	8.00% Notes due 2028
Trading Symbol	GAINL
Security Exchange Name	NASDAQ
7.875% 2030 Notes
Document Information [Line Items]
Title of 12(b) Security	7.875% Notes due 2030
Trading Symbol	GAINI
Security Exchange Name	NASDAQ

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GLADSTONE INVESTMENT CORPORATION\DE 10-Q