Born in St Louis, Byrnes went to Canada during the Vietnam era. Following his accident, he formed the blues group, The Jim Byrnes Band, began playing dates throughout Canada. He broke into the US TV market in 1987 acting in and singing a song he had written for the NBC miniseries "Hands of a Stranger". "Wiseguy", filmed in Vancouver, Canada, premiered later that year. In addition to acting, Byrnes has also done voices for the animated series "Dragon Warrior" (syndicated, 1990) and "Megaman" (syndicated, 1996), appeared in the short-lived syndicated series "Neon Rider" (1990) and performed blues songs on an episode of the HBO series "The Hitchhiker". Byrnes has co-starred in numerous TV movies, beginning with "The Red Spider" (CBS, 1988). He had strong moment playing a war veteran in the award-winning "Serving in Silence: The Margarethe Cammermeyer Story" (NBC, 1995) and reprised the role of Lifeguard for a "Wiseguy" reunion movie on ABC in 1996.
Byrnes' feature film work has been limited, although he earned good notices as a musician in "Harmony Cats" (1994) and is also recalled as a police lieutenant in "Under the Gun" (1995).