His notable works include the disaster novel Nerves (1942; expanded 1956), the dystopian The Eleventh Commandment (1962), and numerous popular juveniles such as The Runaway Robot (1952) and Marooned on Mars (1952), written for the Winston Science Fiction series. Short stories like "Evensong" (1940) and "The Wings of Night" (1941) remain classics of the genre. He also wrote under several pseudonyms, including Philip St. John and Erik van Lhin.
Beyond writing, del Rey was a distinguished editor. After working at several magazines, he and his wife, editor Judy-Lynn del Rey, founded Del Rey Books at Ballantine in 1977. The imprint became one of the most successful SF and fantasy publishers, helping shape the modern publishing landscape.
In recognition of his contributions, del Rey was named a Grand Master by the Science Fiction Writers of America in 1991.