Born in Salt Lake City, Utah, Harline worked for various radio stations before joining the Walt Disney Studios in 1932 as arranger and scorer, and won an Academy Award for the song "When You Wish Upon a Star" from Disney's Pinocchio (1940) which would later become Disney's signature theme for his TV series.

A graduate of the University of Utah, Harline was a musical director for local Los Angeles radio when he was hired by Walt Disney to score the Silly Symphonies cartoon series in the 1930s. With Frank Churchill, Larry Morey, and Paul J. Smith, Harline was responsible for such Disney-film tunes as "I'm Wishing," "Whistle While You Work," "Heigh Ho" and "Some Day My Prince Will Come."

Disney retained Harline's services for his next cartoon feature, Pinocchio (1939) which would lead to his Oscar win. Harline left Disney in 1941 to compose for other studios (among his more memorable projects was the Hope-Crosby comedy Road to Utopia [1945]).