Onstage from 1919, Carnovsky had many distinguished Broadway performances. He debuted onscreen in The Life of Emile Zola (1937), but was in no further films till 1943; then, between 1943-51, he appeared regularly in movies as a character actor. His film career came to a virtual halt during the McCarthy Era "witch hunt" of the early ;50s; in 1951, Carnovsky appeared before the House Un-American Activities Committee and refused to admit or deny past membership in the Communist party, after which he was blacklisted in Hollywood. He did, however, appear in a film or two in the '60s and '70s.