Marshall was born in Gary, Indiana, the son of Thelma (née Edwards) and Vereen Marshall, who was a dentist. He attended New York University as an art student, but then trained for a theatre career at the Actors Studio, at the American Theatre Wing, and with Sanford Meisner at the Neighborhood Playhouse. He made his Broadway debut in 1944 in Carmen Jones. Among his many other Broadway appearances, he understudied Boris Karloff as Captain Hook in Peter Pan in 1950, then played the leading role of De Lawd in the 1951 revival of The Green Pastures (a role he repeated in a BBC telecast of the play in 1958). He performed in Shakespeare plays many times on the stage in the U.S. and Europe, including the title role in at least six productions of Othello. His Othello (which was later captured in a video production in 1981), was called by Harold Hobson of the London Sunday Times “the best Othello of our time. Marshall even played Othello in a jazz musical version, Catch My Soul, with Jerry Lee Lewis as Iago, in Los Angeles in 1968. He also portrayed the roles of Paul Robeson and Frederick Douglass on stage . Marshall had researched Douglass’ life for years and portrayed him on television in Frederick Douglass: Slave and Statesman, which he co-produced in 1983.

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. In later years, Marshall played the King of Cartoons on Pee-wee’s Playhouse, replacing actor Gilbert Lewis, during the 1980s. (The character’s catchphrase “Let…the cartoooon…begin!” became immensely popular.) In the early 1950s, Marshall starred briefly in a series about black police officers, entitled Harlem Detective. The show was canceled when Marshall was named as a communist in the anti-communist newsletter Counterattack.

Despite the blacklisting because of his supposed communist connections, Marshall managed to continue appearing in both television and films. In 1962, Marshall appeared on the British spy series Danger Man in the episode titled “Deadline” and in 1964 Marshall played the role of of travelling opera singer Thomas Bowers on the Bonanza episode “Enter Thomas Bowers.” Additionally in 1964, he appeared, with actor Ivan Dixon, as the leader of a newly independent African nation and as a T.H.R.U.S.H. agent in the first-season episode of The Man from U.N.C.L.E. entitled “The Vulcan Affair”. In 1968 he appeared as Dr. Richard Daystrom in the Star Trek episode “The Ultimate Computer”. In 1969, he had a special guest appearance as the character Amalek in an episode of The Wild Wild West entitled “The Night of the Egyptian Queen”. He also won two local Emmys for producing and performing in a PBS production, As Adam Early in the Morning, a theatre piece originally performed on stage. He also was featured in an episode of The Alfred Hitchcock Hour titled, “The Jar”, with actors Pat Buttram and George Lindsey.

In addition to acting and producing, Marshall taught acting at various universities including the University of California, Irvine, and the Mufandi Institute, an African-American arts and music institution in the Watts section of Los Angeles. He did similar work at Chicago’s ETA Creative Arts Foundation, which in 1992 named Marshall one of its Epic Men of the 20th century. For 42 years, Marshall was the partner of Sylvia Gussin Jarrico, former wife of blacklisted screenwriter Paul Jarrico. Marshall died June 11, 2003, from complications arising from Alzheimer’s disease and diabetes. He was survived by sons Tariq, Malcolm, and Claude Marshall and daughter Gina Loring. Eulogists at his funeral included Sidney Poitier, Ivan Dixon, Paul Winfield, and Marla Gibbs. Marshall was considered by many to be a much underrated actor and one who never got his due. Some have remarked that Marshall should have had a much more successful and larger screen career, even saying that Marshall would have been a perfect choice for the role Thulsa Doom in Conan.