 Mullen, a 6'5 forward from St. Mary's College High School in Berkeley, California, played college basketball at the University of San Francisco from 1951 to 1955.At USF, Mullen teamed with future Hall of Fame center Bill Russell in the frontcourt to bring home the first of the Dons' consecutive national titles in 1955.Mullen was a key player for the team, averaging 13.6 points and 7.1 rebounds per game and earning AP honorable mention All-America honors that year.