Stefano died Aug. 25 at Los Robles Hospital and Medical Center, funeral director Elaine Munoz. The cause of death wasn't disclosed.
Stefano graduated in 1940 from South Philadelphia High School and he went to New York as an aspiring entertainer. He played piano, sang, danced and wrote music and lyrics.
He toured with a modern dance troupe and worked temporary jobs as a typist. He met his future bride, Marilyn Epstein, in a bar in Manhattan in 1953.
"I was trying to make a choice on the jukebox and this great-looking man in black jacket, jeans and boots said, `Play that one, I wrote it,' " she told The Philadelphia Inquirer. They soon married.
Stefano's big TV break came in the 1950s when he was hired as a writer for the "Ted Mack Family Hour." He also wrote a number of scripts, including "The Black Orchid," which was made into a 1958 movie starring Sophia Loren and Anthony Quinn.
Stefano then became a scriptwriter for 20th Century Fox in 1960, and he moved to Hollywood. Hitchcock soon had him adapt a Robert Bloch pulp novel for the screen. The movie became "Psycho."
"Bloch's novel started with Marion Crane arriving at the motel and immediately being killed. My feeling was that, since I did not know anything about this girl, I wasn't going to care about her when she was killed. So we backed the story up a bit and learned something about her so that when she was killed, it would have more impact," Stefano once told the Los Angeles Times.
Stefano had her stealing $40,000 from her boss and stopping at the Bates Motel while on the run. Though she has a change of conscience about the money, Crane is knifed to death in a memorable shower sequence.
He wrote several other screenplays, including "The Naked Edge" with Gary Cooper, but Stefano and screenwriter Leslie Stevens turned to TV to produce and write "The Outer Limits," which ran from 1963 to '65.
Stefano later wrote the 1969 thriller "Eye of the Cat" and co-wrote the comedy "Futz!" that same year with Rochelle Owens.
In the 1970s and 1980s, he wrote TV movies, including "Home for the Holidays" in 1972 and "Snowbeast " in 1977.
Besides his wife, Stefano is survived by his son Dominic. The funeral was private.