Cullen was born in Pittsburgh, Pennsylvania, and survived a childhood bout with polio that left him with a limp for the rest of his life. After moving to New York City he hosted several radio programs, including game shows, in the late 1940s and 1950s. His first TV game show was Winner Take All, a Mark Goodson-Bill Todman production that aired on CBS in 1952. He hosted the highly successful daytime and prime-time versions of The Price is Right, another Goodson-Todman production, from 1956 to 1965.
Cullen hosted 20 different game shows over the years. Some of the shows on that long list include Eye Guess in the 1960s, Three on a Match and the nighttime version of The $25,000 Pyramid in the 1970s, and Blockbusters and The Joker's Wild (his last game show) in the 1980s. He appeared as a celebrity guest on many other game shows throughout his TV career, including I've Got a Secret, Password, To Tell the Truth, Match Game, and the daytime versions of Pyramid that Dick Clark hosted.