In 1991, Margolis played Helmut Dieter in the soap opera Santa Barbara. He has had recurring roles on numerous other TV shows, including The Equalizer, Quantum Leap, Oz, Law & Order, Crossing Jordan, Californication, Breaking Bad, and Better Call Saul. In January 2015, he portrayed Felix Faust in the Constantine episode "Quid Pro Quo". For his role in Breaking Bad and Better Call Saul, Margolis received a nomination for a Primetime Emmy Award for Outstanding Guest Actor in a Drama Series.