In 1943, he moved to New York and soon went out on the road. While working in Atlantic City in 1946, he accidentally partnered with Jerry Lewis. They soon became the hottest act in town. Their popularity grew as they performed across the country and on radio and television. In 1948, they were signed to Capitol Records. In 1949, they made their first in a string of hit movies, My Friend Irma.

The partnership lasted until 1956, when the two went their separate ways. Dean's film career suffered without Lewis at first, but it soon got off the ground with 1958's The Young Lions. He went on to star in several successful films, including a string of Westerns, the Matt Helm spy series, and the 1970 blockbuster Airport.

Dean's solo recording career got off to a slow start. It wasn't until 1953 that he broke into the Top Ten, with the Italian-style novelty tune ''That's Amore.'' In 1955, Dean hit number one for the first time with ''Memories Are Made of This.'' In 1962, Dean left Capitol for Frank Sinatra's Reprise Records. His 1964 recording of ''Everybody Loves Somebody'' became the first song to knock the Beatles out of the number one spot. In 1965, he began hosting his own weekly variety show on NBC. The program was one of the top-rated shows during its nine-year run.

During the late seventies and eighties, he concentrated his career on Las Vegas. In 1987, he joined a Rat Pack reunion tour with Frank Sinatra and Sammy Davis, Jr. but soon withdrew due to health problems. In 1993, it was reported that Dean had lung cancer. He died on Christmas Day in 1995.