- Began acting as a child for Stage Polaris, a theater company in Edmonton.
- Played the younger version of Brad Pitt's character in the film Legends of the Fall.
- Breakout role was as football jock Whitney Fordman on Smallville.
- Participated in the Crazy8 film competition by directing a short film called Candy from Strangers, based on a script written by his wife.
- In 2010, he joined the cast of the crime drama Rookie Blue.
- In 2012, replaced Michael Ironside as the voice of hero Sam Fisher in the Splinter Cell video-game franchise; Johnson calls video-game work "a wholly new process to me."
- Calla Prairie Johnson — Daughter
- Adria Budd — Wife