The son of a famous architect, Californian born and educated Mal St.Clair worked as a cartoonist for the Los Angeles Express before his first movie job as an extra at Keystone in 1915. After service in World War I, he started as a director, alternating between Fox and 'Mack Sennett'. He soon proved to have a penchant for comedy, but could also handle popular action films and, when the occasion demanded, Hollywood's A-grade stars ( Pola Negri in A Woman of the World (1925), Clara Bow in The Fleet's In (1928), Joan Crawford in Montana Moon (1930) etc.). His best collaborations were with star comedians Harold Lloyd and Buster Keaton in the 1920's. He also produced the hit social comedies Are Parents People? (1925) and The Grand Duchess and the Waiter (1926). In 1928, Mal directed an early version of 'Gentlemen Prefer Blondes', but no copies of this film are known to have survived. One of his best non-comedic efforts was the Philo Vance mystery The Canary Murder Case (1929) which starred 'William Powell (I)' , Jean Arthur and Lupe Velez , and won critical plaudits for the director. The New York Times commented (March 11,1929) "his flashes of the canary swinging on a trapeze in a theatre are so excellent that they bring to mind the photographic feats in Variety". St.Clair's career was reinvigorated with the all-star Hollywood Cavalcade (1939), for which he directed the Keystone Kops chase sequences. Between 1943 and 1945, Mal presided over four Laurel & Hardy features at 20th Century Fox in an unsuccessful attempt by the studio to revive the great slapstick comedies of the 1920's. After that his output declined somewhat, except for a few minor films he made for Sol M. Wurtzel's B-unit. At six foot three inches (some say, six foot seven inches), Malcolm St.Clair had the distinction of being known as 'the tallest director in Hollywood'.

Brother of writer/actor Eric St. Clair .Former member of the Keystone Kops .St.Clair's second wife, Margaret Holt, was the daughter of Californian E.M.Murray who invented the sliding ladder for shoe stores.