Manager John Gibbons announced the news before Wednesday's game against the New York Yankees.
Hutchison will pitch in the Blue Jays' second regular-season game Tuesday at Tampa Bay. McGowan beat out several other fifth-starter contenders and is lined up to pitch the home opener against the Yankees on April 4.
McGowan has pitched in just 30 big league games, including 25 relief appearances last season, since right shoulder surgery in July 2008.
"He was one of the top up-and-coming pitchers here in this organization a few years ago," Gibbons said. "It's pretty amazing in my mind that he's come back this far. We're going to run with it and see where it takes us."
McGowan will pitch in a simulated game Sunday, the final step in what he even thought was a long-shot bid to open the year as a starter.
"Excited," McGowan said. "I always had the resolve. There's no quit in my blood. I worked hard to get back. It paid off."
R.A. Dickey will be the starter on opening day on Monday against the Rays. After Hutchison, Mark Buehrle and Brandon Morrow will start the final two games of the four-game series with Tampa Bay.
Left-hander J.A. Happ, who was in the mix for the final rotation spot, will start the season on the disabled list with back tightness.
Gibbons said other starting candidates, Todd Redmond, Esmil Rogers and Jeremy Jeffress, will work out of the bullpen.
Also, Josh Thole beat out Erik Kratz for the backup catcher role. Thole will catch his former New York Mets teammate, the knuckleballing Dickey.