McLeod became an animator and writer for the comedy shorts of producer Al Christie by the late teens. A combat pilot for the Royal Canadian Air Force during World War One, he was brought in to assistant direct on William A. Wellman's Wings in 1927. The following year he helped script The Air Circus for co-directors Howard Hawks and Lewis Seiler; he also helmed his first feature, Taking a Chance. After co-directing films with Lloyd Corrigan (Along Came Youth) and Norman Taurog (Finn and Hattie), McLeod began presiding over some of the funniest films of the early '30s: Monkey Business and Horse Feathers with the Marx Brothers, and It's a Gift with W.C. Fields. His other work of the decade includes the fantasies Alice in Wonderland and Topper. Notable among his comedies and musicals of the '40s and '50s are his films with Danny Kaye (The Kid from Brooklyn, The Secret Life of Walter Mitty) and Bob Hope (Road to Rio, The Paleface, My Favorite Spy, Casanova's Big Night, Alias Jesse James).