Authorities said Monteith, 31, was found dead in his room at noon local time at the Fairmont Pacific Rim Hotel.
Hotel staff checked his room when he missed his checkout time, and discovered the body. He had been dead for several hours before he was found.
The cause of death was not immediately apparent but police said there were no indications of foul play. They would not comment on speculation that he had died of a drug overdose.
Monteith had been out earlier in the night but returned to the room alone, police said.
Acting Chief Doug LePard told a news conference: "There were others with Mr Monteith in his room earlier last night, but video and fob key entries show him returning to his room by himself in the early morning hours and we believe he was alone when he died."
An autopsy has been scheduled for Tomorrow.