He played junior hockey with the Chicago Blackhawks-sponsored St. Catharines TeePees of the Ontario Hockey Association from 1951-54, winning the Memorial Cup in 1954. In that season, he was also the leading score, outstanding player, and first team all-star. He was traded to the Toronto Maple Leafs in 1954. Cullen began his National Hockey League career with Toronto in 1954. He spent three seasons there. After that he played for the New York Rangers for two more.