Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 01, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	Acer Therapeutics Inc.
Entity Central Index Key	0001069308
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Trading Symbol	ACER
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		10,095,176
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2019
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-33004
Entity Tax Identification Number	320426967
Entity Address, Address Line One	One Gateway Center
Entity Address, Address Line Two	Suite 351
Entity Address, Address Line Three	300 Washington Street
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