Mitchell led the Stampeders to victory in the 106th Grey Cup to cap off an incredible campaign, and he was named the game's most valuable player.
The 28-year-old became Calgary's starting quarterback in 2014 and has developed into arguably the league's premier player. He led the CFL with 35 touchdown passes in 2018.
Mitchell was highly sought after as a free agent, reportedly receiving contract offers from the Toronto Argonauts and Saskatchewan Roughriders.
The signal-caller worked out for the NFL's Minnesota Vikings in December, but he didn't sign a contract.
Mitchell is a two-time CFL All-Star, and a two-time winner of the Most Outstanding Player award.