This netted Marlon Brando his third consecutive Best Actor Oscar nomination. He had previously been nominated for Endstation Sehnsucht (1951) and Viva Zapata (1952).
Sir John Gielgud was cast after director Joseph L. Mankiewicz saw him play Cassius in a stage production at Stratford-upon-Avon. Mankiewicz was in Stratford to see Paul Scofield, who he was considering casting as Mark Antony, until Marlon Brando's screentest turned out so well.
Director John Huston described Brando's intense Method acting in the film as "like a hot furnace opening in a dark room."
This movie was shot in just 35 days, using some of the sets from Quo vadis? (1951), which were dismantled, flown from Rome to Hollywood, and then reassembled for this film. Producer John Houseman confirmed that it was never intended that the movie be shot in color, as he and director Joseph L. Mankiewicz wanted it to have the urgency of a newsreel, not to look like a costume epic.
Marlon Brando became good friends with John Gielgud during filming and frequently sought Gielgud's advice on how to speak the blank verse. Gielgud invited Brando to come to London to star in a Shakespeare season on the West End stage under his direction, but it never happened.