Document and Entity Information - shares
3 Months Ended
Mar. 31, 2019
Jun. 14, 2019
Document and Entity Information [Abstract]    
Entity Registrant Name Milestone Pharmaceuticals Inc.  
Entity Central Index Key 0001408443  
Document Type 10-Q  
Document Period End Date Mar. 31, 2019  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   24,490,742
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Entity Shell Company false