Born in Boston, Haley began as a song-and-dance man and appeared on Broadway in the hits "Good News" and "Gay Paree". He made his first foray into movies in the silent "Broadway Madness" (1927) and returned three years later as a Paramount player in "Follow Thru" (1930). It wasn't until he was signed by Fox, though that he came into his own as a genial second lead in such efforts as "Poor Little Rich Girl" (1936) and "Rebecca of Sunnybrook Farm" (1938), both with Shirley Temple, and "Alexander's Ragtime Band" (also 1938). Haley was loaned to MGM to play the coach in "Pigskin Parade" (1936), which also marked the debut of Judy Garland and again to replace an ill Buddy Ebsen (who had an allergic reaction to the makeup) in "Oz". (Ironically, Ray Bolger was originally slated for the role but he balked and managed to convince the studio to allow he and Ebsen to switch roles.) Haley, along with Bolger and Bert Lahr, all shared similar professional backgrounds having played vaudeville and burlesque as well as the legitimate stage and worked well together. Nonetheless, he was a bit overshadowed by the showier antics of his co-stars and by the luminous tremulousness that Judy Garland brought to her role. Still, because "The Wizard of Oz" achieved classic status with repeated TV broadcasts, it remains his best-remembered role.
In the 1940s, Haley continued to lend support to major stars in films like "Moon Over Miami" (1941), with Betty Grable and Don Ameche, and "Higher and Higher" (1943), with Frank Sinatra. But as the decade wound down and he inched toward his 50s, he was virtually wasted in fluff (i.e., "Scared Stiff" 1945). He retired from show business after "Make Mine Laughs" (1949), which reunited him with Ray Bolger, and a brief stint as host of TV's "Ford Star Revue" (NBC, 1950), finding a lucrative second career in real estate. His son, Jack Haley Jr., persuaded him to come out of retirement for a one-shot return to features with a cameo in 1970's "Norwood". Although there were occasional TV roles (e.g., the ABC movie "Rolling Man"), the elderly Haley seemed uninterested in pursuing a career as a character actor, preferring to be remembered for his earlier work.