Provincial police Sgt. Gino Pare says the incident happened late Monday afternoon when city police answered a call from a woman in distress.
He says when Montreal police officers arrived, they were attacked by a man and that he was left lying unconscious on the ground.
The victim, who has been identified as Donald Menard, was taken to hospital where he was pronounced dead.
There are reports that some form of electronic device was used by police, but Pare would only say that no firearms were involved.
He said officers used other means which could have been batons or pepper spray.
Authorities are awaiting medical expertise to determine the exact cause of death.
Four officers were injured during the confrontation, with one suffering head injuries.