| Cover - USD ($) $ in Millions | 12 Months Ended | ||
| Dec. 31, 2023 | Mar. 21, 2024 | Jun. 30, 2023 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | false | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Document Period End Date | Dec. 31, 2023 | ||
| Document Fiscal Period Focus | FY | ||
| Document Fiscal Year Focus | 2022 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity File Number | 001-38899 | ||
| Entity Registrant Name | Milestone Pharmaceuticals Inc. | ||
| Entity Central Index Key | 0001408443 | ||
| Entity Tax Identification Number | 00-0000000 | ||
| Entity Incorporation, State or Country Code | A8 | ||
| Entity Address, Address Line One | 1111 Dr. Frederik-Phillips Boulevard | ||
| Entity Address, Address Line Two | Suite 420 | ||
| Entity Address, City or Town | Montréal | ||
| Entity Address, State or Province | QC | ||
| Entity Address, Postal Zip Code | H4M 2X6 | ||
| City Area Code | 514 | ||
| Local Phone Number | 336-0444 | ||
| Title of 12(b) Security | Common Shares | ||
| Trading Symbol | MIST | ||
| Security Exchange Name | NASDAQ | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Non-accelerated Filer | ||
| Entity Small Business | true | ||
| Entity Emerging Growth Company | true | ||
| Elected Not To Use the Extended Transition Period | true | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 95.9 | ||
| Entity Common Stock, Shares Outstanding | 53,149,778 | ||
| ICFR Auditor Attestation Flag | false | ||
| Document Financial Statement Error Correction [Flag] | false | ||
| Auditor Name | PricewaterhouseCoopers LLP | ||
| Auditor Location | Montreal, Canada | ||
| Auditor Firm ID | 271 |
