The crash happened around 1 a.m. at the corner of Jean-Talon and Garnier streets when a car carrying five people travelled down the wrong side of the street, hitting a taxi carrying two passengers.
The 53-year-old driver of the cab and one of his fares, a 33-year-old man seated in the front passenger seat, sustained serious, but not life-threatening, leg injuries.
Three people in the other car were injured, though one of them suffered only minor injuries.
Const. Simon Delorme of the Montreal police said early evidence suggests alcohol and speed were factors, and the 29-year-old driver will have to undergo a blood test.