- Played on his high school's baseball and football teams.
- Attended college on a music scholarship.
- Considered becoming a physical therapist.
- Broke into acting when movie Benny & Joon (1993) filmed in Spokane, WA, and he served as a stand-in for Aidan Quinn.
- Made his big-screen debut with a small role in the 1995 thriller Crimson Tide.
- In 2001, started a fitness company, Bioconstructs, which teaches biomechanics to fitness professionals.
- Was passed over for the role of Kevin Buchanan on One Life to Live, but in 2003, won the part of Walker Laurence/Todd Manning.
- As a jazz percussionist, has played with musicians such as Marshall Royal, Slide Hampton, Bill Berry and Gene Harris.
- Has put his drum skills on display at ABC Super Soap Weekend events.
- Won Best Actor at the NYC Downtown Short Film Festival and the Staten Island Film Festival for his performance in the short The Art of Getting Over It (2009), which he also co-wrote and co-produced.
- Practices Tibetan Buddhist meditation.
- Mark St. John — Father
- Aiden Lee St. John — Son
- Sara St. John — Wife
- Whitworth College, Spokane, Washington, United States (BA in Theatre, 1993)