A veteran of vaudeville, Conlin performed with his wife, Myrtle Glass. Entering films in the 1920s, he appeared in over one hundred shorts and feature films, often in B comedies or mysteries. He was frequently cast as doormen, piano players, and bums. Notable appearances includeed Rose-Marie (1936, as the piano player, with Nelson eddy and Jeanette MacDonald), My Little Chickadee (1940 as bartender Squawk Mulligan opposite W.C. Fields), Charlie Chan at the Wax Museum (1940), The Picture of Dorian Gray (1945), Dick Tracy's Dilemma (1947, as "Sightless"), and Anatomy of a Murder. On television, he played Jimmy the waiter on Duffy's Tavern and appeared in an episode of Philip Marlowe.