Mark Valley first became interested in acting during high school, but put his aspirations on hold when he decided to attend West Point. He graduated with a degree in math and was then stationed in Germany, where he stayed for five years ? except for the time he spent participating in Operation Desert Storm.

His acting career began when he was discovered by an agent in Berlin. His first role was working in John Schlesinger's The Innocent, which starred Anthony Hopkins and was filmed in Germany. He continued working abroad and appeared in several more productions before returning to the United States to pursue his career further.

Valley made an impact on television viewers with his lead role in Pasadena, as well as in recurring roles on ER and Once and Again. Additional television work includes guest spots on CSI, The Lone Gunmen and Gideon's Crossing, as well as a stint on the long-running daytime drama, Days of Our Lives. He also appeared in several telefilms, including Running Mates and Breast Men, and portrayed Senator Robert Kennedy in George Wallace.