Shortly after 9 p.m., a patrol car spotted a 23-year-old man lying on Henri-Bourassa Boulevard, near the corner of Sackville Street.
Witnesses at the scene told police the victim was hit by the car and thrown about 20 metres.
The driver then fled the scene.
The victim is in hospital with serious head injuries.
Const. Raphael Bergeron said police are searching for a small, silver vehicle.
"It is impossible to determine exactly what type of vehicle it is, but we know that it is a small compact vehicle that was involved due to the description that we have [from] different witnesses," Bergeron said.
Anyone with information is asked to call the Info-Crime hotline at 514-393-1133.