Mandylor's first major role was in the 1989 film Triumph of the Spirit playing a European Jew, which was filmed at the Auschwitz-Birkenau death camp. He returned to Los Angeles meeting director Oliver Stone and auditioned and got the role of an Italian count in The Doors (1991). Mandylor landed a leading role in Mobsters playing Mafia boss Frank Costello. He went mentally prepared for the role, telling the Los Angeles Times, "It was interesting that I got that part, because I felt tuned in to gangsters, it was a genre I'd read a lot. When I was 13, I got a job as a dishwasher in a Melbourne nightclub and saw everything there, real gangsters, and had met characters who were dangerous people from an underground world." In 1992 he had a lead role on the CBS television drama, Picket Fences, playing officer Kenny Lacos until the show ended in 1996. Mandylor also had a lead role in the Saw films as Detective Mark Hoffman.