According to witnesses, a car made an illegal left turn onto St-Joseph Boulevard from St-Denis Street and crashed into another vehicle around 5:30 p.m. on Christmas day.
One of the two cars involved in the crash then hit a pedestrian who was walking on the sidewalk.
Four people were injured, including the pedestrian, and were transported to hospital. One of the injured is a teenager.
Const. Danny Richer of Montreal police said some of those who were involved were seriously injured, although their lives are not in danger.
Police are investigating.