With several decades of experience as a stage actor, he is especially acclaimed as an interpreter of the works of Samuel Beckett.
[2] He acted on stage in both Canada and the United States, building a reputation in San Francisco's theater scene in the 1950s.
[2] Mandell's association with Beckett began in 1957, with a production of Waiting for Godot at the San Francisco Actor's Workshop.
[4] Outside of Beckett, Mandell has acted in productions of Harold Pinter's No Man's Land and Arthur Miller's The Price.
[3] In 2007 he appeared as Juror #9 in a Los Angeles production of Twelve Angry Men, directed by Scott Ellis and costarring Richard Thomas and George Wendt.