Police say one man in his 30s died at the scene and the second victim, also in his 30s, died later in hospital.
The third victim, in his 20s, suffered non life-threatening injuries.
Police spokesman Danny Richer says a person in his 20s was arrested nearby but it was unclear if this person was a suspect.
The shooting occurred in a bar at about 6:15 p.m. (on Newman Blvd.).
The deaths are Montreal’s 14th and 15th homicides of the year.