Quarterly report pursuant to Section 13 or 15(d)

Document And Entity Information

Document And Entity Information - shares
6 Months Ended
Sep. 30, 2021
Nov. 10, 2021
Document Information [Line Items]    
Entity Central Index Key 0001444192  
Entity Registrant Name Acasti Pharma Inc.  
Amendment Flag false  
Current Fiscal Year End Date --03-31  
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2021  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2021  
Document Transition Report false  
Entity File Number 001-35776  
Entity Incorporation, State or Country Code CA  
Entity Tax Identification Number 98-1359336  
Entity Address, Address Line One 3009 boul. de la Concorde East, Suite 102  
Entity Address, City or Town Laval  
Entity Address, State or Province QC  
Entity Address, Country CA  
Entity Address, Postal Zip Code H7E 2B5  
City Area Code 450  
Local Phone Number 686-4555  
Title of 12(b) Security Common Shares, no par value per share  
Trading Symbol ACST  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   44,288,183