Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 01, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	Acer Therapeutics Inc.
Entity Central Index Key	0001069308
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 21,551,439
Entity Common Stock, Shares Outstanding		10,095,176
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	ACER
Security Exchange Name	NASDAQ
Entity File Number	001-33004
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0426967
Entity Address, Address Line One	One Gateway Center
Entity Address, Address Line Two	Ste. 351
Entity Address, Address Line Three	300 Washington St.
Entity Address, City or Town	Newton
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02458
City Area Code	844
Local Phone Number	902-6100
Document Annual Report	true
Document Transition Report	false