He directed James Dean, Louis Jourdan and Geraldine Page in the Broadway production of The Immoralist. When Elia Kazan saw James Dean in The Immoralist he cast Dean in East of Eden.
He was one of the first teachers at the Actors Studio in New York along with Elia Kazan, and Stanford Meisner.
He studied acting with Sanford Meisner at the Neighborhood Playhouse and
eventually became his assistant. In the very early days of the Actors
Studio (founded in 1947) before Lee Strasberg became its artistic
director, Mann was one of its first teachers.