A native of St. Louis, Missouri, Susman graduated from Ladue Horton Watkins High School in 1965.

In a 1971 news article, Susman mentioned he moved to Los Angeles because a friend told him he could make $500 a week as a writer. Unfortunately, the plan did not go well and he ended up making $60 a week as a writer for American International Pictures.

In 1976, he was a regular on the six-episode CBS adventure series Spencer’s Pilots. He portrayed Ted Lapinsky in The Waltons (the episodes ‘The Home Front’ (1979) and ‘The Unthinkable” (1980)) and appeared as detective Spade Marlow in the 1991 episode of The Golden Girls titled “The Case of the Libertine Belle”. Before that, Susman submitted a pilot series for Grant Tinker for MTM Enterprises about an innocent young man arriving in New York City to start his career. Other television shows Susman has appeared on since 1971 include Love, American Style (3 episodes), Room 222 (3 episodes), Kojak, Eight Is Enough, The White Shadow, M*A*S*H (in addition to the 46 episodes in which he provided the voice of the announcer on the camp’s P.A. system), The Waltons (3 episodes), Little House on the Prairie, Lou Grant, Remington Steele, Alice, Hill Street Blues, The Facts of Life, Cagney & Lacey, Night Court (3 episodes), Who’s the Boss?, Punky Brewster (3 episodes), Webster (4 episodes), ALF, Highway to Heaven, Murder, She Wrote, The Golden Girls, Blossom (2 episodes), Married… with Children, The Commish, ER, Suddenly Susan, Law & Order, Law & Order: Special Victims Unit, and Bull.

Susman has one child with his first wife Judy, who is a working actress. He married Bella Kordonov on November 6, 1982; they have three children.

In addition, he appeared in the TV Movies Death Scream (1975), Portrait of an Escort (1980), Thornwell (1981), The Other Victim (1981), City Killer (1984), I Married a Centerfold (1984), The Guardian (1997), The Superagent (2009) and You Don’t Know Jack (2010). He portrayed Sergeant Dobbs in the 1986 TV mini-series Fresno.

Susman has appeared in over one hundred different television series and commercials and was also featured in the Broadway production of Hairspray, the 1970s films Star Spangled Girl (1971), The Loners (1972), Little Cigars (1973) and California Dreaming (1979). He later appeared in the major studio films Beverly Hills Cop II (1987), Coneheads (1993), The Juror (1996), and the remake of The Taking of Pelham 123 (2009). Susman was in the 2007 independent film, The Big Bad Swim, and the 2009 comedy, The Flying Scissors. He also voiced the lead character in the 2002 video game Soldier of Fortune II: Double Helix.

In 2012, Susman appeared in the original cast of the off-Broadway Westside Theatre show, “Old Jews Telling Jokes”, in which Jessica Shaw of Entertainment Weekly called his portrayal “the funniest moment…delivered with a Yiddish accent as thick as schmaltz”. Jason Zinoman of The New York Times also complimented his performance, saying “the incongruity between content and form is perfectly tuned, and Mr. Susman benefits from resisting the urge to oversell the joke”. David Finkle of TheaterMania.com also said Susman “often scores simply through his feigned stoicism”.

In 2013, Susman, along with the Old Jews Telling Jokes cast and The Chew personality Carla Hall appeared at Carnegie Deli to unveil the “OJTJ sandwich”, named for the comedy group.