Bettger's theatrical debut was in Brother Rat at the Biltmore Theatre in New York City in 1936. His Broadway credits include Dance Night (1938), Summer Night (1939), The Flying Gerardos (1940–1941), The Moon Is Down (1942), All for All (1943), Oh, Brother! (1945), John Loves Mary (1947–1948), and Love Life (1948–1949).
Bettger's movie career began when he was cast in The Lie in 1949. Movie columnist Frank Neill reported, "On the basis of his performance in the movie, he has been signed to a juicy contract."
Later Bettger was cast as the lead in the film noir No Man of Her Own (1950). He soon became a regular on the set of Westerns such as Denver and Rio Grande (1952), The Great Sioux Uprising (1953), Forbidden (1953), Drums Across the River (1954), Destry (1955), The Lone Ranger, (1956) and Gunfight at the O.K. Corral (1957). Lyle developed a reputation for playing the bad guy and excelled in villainous roles such as the menacing Joe Beacom in Union Station (1950) and the cold-blooded Nazi Chief Officer Kirchner in The Sea Chase (1955). One of his later roles was in the 1969 film Impasse as a bigoted World War II veteran.
Bettger made many appearances in dramatic roles on television, starring in the 1957 series The Court of Last Resort as well as guest starring on Hawaii Five-O, Rawhide, The Tall Man, The Rifleman, Gunsmoke, Bonanza, Blue Light, and The Time Tunnel.
Bettger was married to Mary Rolfe (1940–1996), an Actress who played Henry Aldrich's sister in The Aldrich Family on radio, until her death. They had three children: Lyle, Jr., Frank, and Paula. He died on September 24, 2003 in Atascadero, California aged 88. His remains were cremated. He was survived by his children and a sister.
