Guy Endore was born Samuel Goldstein in New York City. His father was a coal miner, inventor, and investor from Pittsburgh who often had difficulty making ends meet. His mother committed suicide when he was four, and after her death his father changed the family's names and placed the children in a Methodist orphanage. When his father made some money with one of his inventions, he sent the children to Vienna, where they lived for five years under the care of a Catholic governess. Then his father disappeared, the money ran out, and he returned to Pittsburgh. He went to Columbia University and received a B.A. in 1923 and an M.A. in 1925, both in European languages. After graduating, he married Henrietta Portugal. His first book, Casanova: His Known and Unknown Life, was published in 1929. He and his wife moved to Hollywood, California, and in 1935 he became a screenwriter in addition to writing novels. He gained a reputation for his work on horror films.
