Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2021	Feb. 07, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Document Transition Report	false
Entity File Number	333-252262
Entity Registrant Name	Hanover Bancorp, Inc. /NY
Entity Central Index Key	0001828588
Entity Incorporation, State or Country Code	NY
Entity Tax Identification Number	81-3324480
Entity Address, Address Line One	80 East Jericho Turnpike
Entity Address, City or Town	Mineola
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	11501
City Area Code	516
Local Phone Number	548-8500
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		5,828,203