Marshall's career on screen began in the 1952 film "Lydia Bailey" as a Haitian leader. He followed that with a prominent role as Glycon, comrade and fellow gladiator to Victor Mature in the 1954 film "Demetrius and the Gladiators". His demeanor, voice and stature gave him a wide range, though he was ill-suited for the subservient roles that many black actors of his generation were most frequently offered. He was a leader of the Mau-Mau uprising in "Something of Value" (1957), and Attorney General Edward Brooke in "The Boston Strangler" (1968). He probably received the most notice for his role in the vampire film "Blacula" and its sequel "Scream Blacula Scream".