Marts began his NFL career as a free agent from Tulane University where he had a position as a safety, despite his large frame. In 1991, he was discovered by Tony Dungy and signed with the Kansas City Chiefs. He later played with the Tampa Bay Buccaneers from 1994 to 1996. Many believe that during this time is when he was at his best performance. He later played with the Tennessee Oilers and started 15 games with the team until 1998. In 1999, Lonnie played with the Jacksonville Jaguars and replaced the injured Bryce Paup. He retired with the Jaguars in 2000.
