He was one of the founders of the Group Theatre (1931-1940) in New York City and had a thriving acting career both on Broadway and in films until, in the early 1950s, professional colleagues told the House Un-American Activities Committee that Carnovsky had been a Communist Party member.

Two years later, Carnovsky joined the Theatre Guild acting company and appeared in the title role of Uncle Vanya (by Anton Chekhov).

[5][6] Carnovsky appeared in almost every major Group Theatre production, often playing parts that had been written specifically for him by his good friend, the actor and playwright Clifford Odets.

Among Carnovsky's major triumphs at the Group Theatre were the Odets plays Awake and Sing, Golden Boy, Paradise Lost and Rocket to the Moon.

[citation needed] He also appeared in the anti-war musical Johnny Johnson, Sidney Kingsley's Men in White, the Elia Kazan-directed Thunder Rock, My Sister Eileen, and Cafe Crown.

Writing about the Group's production of Awake and Sing!, the New York Times critic Brooks Atkinson said, "...Morris Carnovsky as the lonely old sage struggling with ideas he cannot resolve or use, gives a performance worth a mayor's reception on the steps of City Hall.

Carnovsky's movie debut came in the Academy Award-winning best picture of 1937, William Dieterle's The Life of Emile Zola starring Paul Muni.

It was followed by a supporting role in Anatole Litvak's Tovarich, before Carnovsky returned to New York and a newly re-configured formation of the Group Theatre.

[8] In 1943, he played a retired Norwegian school teacher, Sixtus Andresen, in the Warner Bros. anti-Nazi film, Edge of Darkness, which starred Errol Flynn and was directed by Lewis Milestone.

Carnovsky portrayed George Gershwin's father in Rhapsody in Blue in 1945, and in Dead Reckoning (1947), he starred as the villainous nightclub owner Martinelli with Humphrey Bogart.

[citation needed] On Broadway, Carnovsky appeared alongside Fredric March in Ibsen's An Enemy of the People, adapted by Arthur Miller, in the 1950-51 season.

[12] Actor Sterling Hayden testified before HUAC that he had attended Communist Party meetings that were sometimes held at Carnovsky's house in Hollywood.

Culled by Christopher Burstall and Stuart Hood from 23,000 pages of the original transcript, the program is a 1970 co‐production of the British Broadcasting Corporation and Bavarian Television.

[20] In 1980, he served on the artistic advisory board of the Yiddish National Theatre, a nonprofit effort to promote awareness of an increasingly forgotten part of stage history.

[21] In the 1980s, Carnovsky was an instructor of Shakespearean acting at the National Theater Institute, at the Eugene O'Neill Theater Center in Waterford, CT. A highly acclaimed performance at Stratford Shakespeare Festival in King Lear led to something of a second career for Carnovsky as a mentor of young actors, as he traveled to universities all over the country, playing the leading roles of Lear, Falstaff, and Shylock in the Shakespeare classics with supporting casts made up of college students.