At around 1:30 a.m. residents in nearby Île-Bizard called 911 after hearing a man crying for help.
Police found the 24-year-old man clinging onto a pillar and fighting the strong current under the Jacques-Bizard Bridge.
Const. Jean-Pierre Brabant of Montreal police said a nearby resident with a boat offered his help to give a life jacket.
The man was pulled from the water by firefighters nearly an hour later.
He was taken to hospital as a preventative measure after having spent more than an hour in cold waters.
Brabant said the man had been drinking.