Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	Athira Pharma, Inc.
Entity Central Index Key	0001620463
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		37,222,666
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-39503
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-3368487
Entity Address, Address Line One	18706 North Creek Parkway,
Entity Address, Address Line Two	Suite 104
Entity Address, City or Town	Bothell,
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98011
City Area Code	425
Local Phone Number	620-8501
Document Quarterly Report	true
Document Transition Report	false
Security12b Title	Common Stock, $0.0001 par value per share
Trading Symbol	ATHA
Security Exchange Name	NASDAQ