[3] In 1946, Long was cast in his first film, Tomorrow Is Forever, as Drew, the son of the characters played by Claudette Colbert and Orson Welles.

[6] International was going to lend Long to 20th Century Fox to make Margie (1946), but then they changed their minds and put him in The Dark Mirror (1946) starring Olivia de Havilland and Thomas Mitchell and directed by Robert Siodmak.

Long signed a contract with Universal, for which he appeared in Tap Roots (1948) and Criss Cross (1949), playing Burt Lancaster's brother in the latter for Siodmak.

He was the juvenile lead in Back at the Front (1952) and had supporting parts in All I Desire (1953), All American (1953) (as the villain to Tony Curtis's hero), Saskatchewan (1954), and Playgirl (1954).

Long began guest-starring on TV shows such as Lux Video Theater ("I'll Never Love Again") and was finally given a lead role by Universal in Cult of the Cobra (1955) – though still billed under Faith Domergue.

Long focused on television over the next few years, guest-starring on episodes of shows such as Climax!, Screen Directors Playhouse, TV Reader's Digest, The United States Steel Hour, Hey, Jeannie!, Schlitz Playhouse, Suspicion, Alcoa Theatre, Wagon Train, Have Gun – Will Travel, The Millionaire, Matinee Theatre, The Twilight Zone episodes ("Number 12 Looks Just Like You" and "Person or Persons Unknown"), and The Further Adventures of Ellery Queen.

He played the recurring role of gambler/con artist Gentleman Jack Darby in four episodes of the ABC/WB Western series, Maverick beginning in 1958, including the memorable "Shady Deal at Sunny Acres" installment.

Warner Bros. starred Long in a show, Bourbon Street Beat (1959–60) as Rex Randolph, Private Eye, which only ran for 39 episodes.

[citation needed] He returned to films with a role in the MGM romantic musical Follow the Boys, along with co-stars Connie Francis, Paula Prentiss, and Roger Perry.

In 1963, Long guest-starred in the episode "Hear No Evil" of ABC's Going My Way, a drama series starring Gene Kelly about a Catholic priest in New York City loosely based on the 1944 Bing Crosby movie.

Long served in the U.S. Army for two years during the Korean War,[21] where he was posted to Fort Ord, California, alongside actors Martin Milner, David Janssen, and Clint Eastwood.

[34] After a month-long stay in Tarzana Medical Center in Los Angeles to treat additional attacks, he died on December 21, 1974, four days after his 47th birthday.