Prior to entering acting, Matheson served in the military. While serving in Korea, he was awarded the Bronze Star for valorous leadership and a Purple Heart for injuries suffered in an explosion. After serving six years, he joined the Detroit Police Department. He then left law enforcement to begin a career in acting.
After working in a number of plays, television episodes and commercials, Matheson was signed to join the cast of the Land of the Giants. He married co-star Deanna Lund in 1970, but they were divorced in the late 1970s.