Monteith was born in Calgary, Alberta and raised in Victoria, British Columbia. He had one older brother. His parents divorced when he was 7 years old. He lived with his mother in Calgary, Alberta, with his father living in Oromocto, New Brunswick. Before becoming an actor, he worked in Nanaimo, British Columbia as a Wal-Mart people greeter, at a car wash, taxicab driver, school bus driver and roofer.