Police said the event took place at a restaurant north of Jean Talon Street.
They said the man entered the restaurant shortly after 5 a.m. and seemed agitated and possibly inebriated.
Authorities said customers tried to calm the man. At some point, another man stabbed him in the upper body.
The 31-year-old suspect fled the scene on foot but was arrested by police soon after.
The suspect also suffered injuries to his upper body. He was taken to hospital but authorities said his life is not in danger.
Investigators will be meeting with him today.