He also played sympathetic roles, however, as in Imitation of Life, in which he portrayed Claudette Colbert's love interest. He appeared as her love interest again that year, when he played Julius Caesar to her Cleopatra in Cecil B. DeMille's version of Cleopatra. And he was the swashbucking D'Artagnan in the 1939 version of The Man in the Iron Mask, directed by James Whale.
William was the first to portray Earl Stanley Gardner's fictional defense attorney Perry Mason on the big screen and starred in four fast paced, comical, and highly entertaining Perry Mason mysteries. He also played Raffles-like reformed jewel thief The Lone Wolf for Columbia Pictures beginning with The Lone Wolf Spy Hunt (1939) with Ida Lupino and Rita Hayworth, and he starred as detective Philo Vance in two films in that series, 1934's The Dragon Murder Case and 1939's The Gracie Allen Murder Case (billed below Gracie Allen).
For his contribution to the motion picture industry, Warren William has a star on the Hollywood Walk of Fame at 1551 Vine Street.