He has an older sister, Melinda, and a younger sister, Deborah. McMahon was educated at Sydney Grammar School, a private boys school. in addition to a career as a fashion model, including a jeans commercial for Levi Strauss, McMahon began an acting career on Australian soap Home and Away, playing the soldier Ben Lucini (1989-1991). From 1996 to 2000, he starred in all four seasons of the NBC drama Profiler as Agent John Grant. Following Charmed, McMahon’s next role was playboy plastic surgeon Christian Troy on the FX series Nip/Tuck.
