Montreal police Const. Danny Richer said one of the vehicles ran a red light at the corner of Parc Avenue and Prince Arthur Street at about 3:30 a.m.
Richer said one car, heading south on Parc Avenue, slammed into another vehicle crossing the intersection. The southbound vehicle then collided with another car heading north.
Two people were sent to the hospital with serious injuries and three others in the northbound car were treated for minor injuries.