Document And Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2021	Sep. 10, 2021	Dec. 31, 2020
Document And Entity Information
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2021
Entity File Number	0-10004
Entity Registrant Name	NAPCO SECURITY TECHNOLOGIES, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	11-2277818
Entity Address, Address Line One	333 Bayview Avenue
Entity Address, City or Town	Amityville
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	11701
City Area Code	631
Local Phone Number	842-9400
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	NSSC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000069633
Current Fiscal Year End Date	--06-30
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 376,476,776
Entity Common Stock, Shares Outstanding		18,351,084