Long also played private detective Rex Randolph as a series lead in both Bourbon Street Beat and 77 Sunset Strip, replacing Roger Smith in the latter show when Smith had to drop out due to health problems.
Early in his career he appeared in several films as a juvenile lead, including a series of Ma and Pa Kettle movies as one of their sons, Tom Kettle. His second film was the Orson Welles film The Stranger as Noah, the brother of Loretta Young's character. He also played "Jeff Taylor" in The Life of Riley. He then moved into leading man status in B movies such as House on Haunted Hill (1959) before finally achieving success in television. One of his final appearances on television was on the game show Match Game in 1974.

His wife of fourteen months, actress Suzan Ball (a cousin of Lucille Ball) died of cancer in 1955, aged only 21. In 1957, Long married actress and model Mara Corday with whom he remained until his early death at the age of 47 from multiple heart attacks in 1974.