Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 23, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	LRMR
Entity Registrant Name	LARIMAR THERAPEUTICS, INC.
Entity Central Index Key	0001374690
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		17,710,450
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-36510
Entity Tax Identification Number	20-3857670
Entity Address, Address Line One	Three Bala Plaza East
Entity Address, Address Line Two	Suite 506
Entity Address, City or Town	Bala Cynwyd
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19004
City Area Code	844
Local Phone Number	511-9056
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Document Annual Report	true
Document Transition Report	false
Entity Incorporation State Country Code	DE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 94.4
ICFR Auditor Attestation Flag	false
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K incorporates certain information by reference from the registrant’s proxy statement for the 2022 annual meeting of shareholders to be filed no later than 120 days after the end of the registrant’s fiscal year ended December 31, 2021.
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Philadelphia, Pennsylvania, USA