Segall was born in Chicago.
Harry Segall's writing career spans 1933 to1959. Segall's plays, including Lost Horizons, appeared on Broadway in the mid-1930s. In 1933, Metro-Goldwyn-Mayer brought Segall to Hollywood as a contract writer. In 1936 he moved to RKO Radio Pictures where he wrote and co-wrote screenplays for films such as Outcasts of Poker Flat, based on a story by Bret Harte and Blind Alibi, starring Richard Dix. During this time, Paramount Pictures and Universal Studios also produced his screenplays. In 1941 Segall won an Academy Award for best original story for the film Here Comes Mr. Jordan, starring Robert Montgomery, based on his play Heaven Can Wait. A 1978 film version of Heaven Can Wait starred Warren Beatty which was subsequently remade several times under various titles, most recently in 2001 starring Chris Rock.
With the advent of television, Segall turned his writing talents to this medium, writing plots for TV series and Playhouse 90. He retired from screenwriting in 1959 and died in Woodland Hills, California 1975.