The Boeing 737 was flying in from Toronto, said Marie-Claude Deschenes, a spokeswoman for the agency that oversees Pierre Elliott Trudeau International Airport.
While there was no immediate word on what caused the plane to skid, it had been raining heavily before the incident.
Deschenes said airport operations were not affected and that no flights were delayed.
Westjet (TSX:WJA) said in a tweet that Flight WS588 exited the runway onto nearby grass and that everyone was reported safe.
The airline later tweeted that all passengers had safely disembarked.
The federal Transportation Safety Board was called in to investigate.
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