costello was noticed by scouts as a teen and was convinced by his older brother les, to enrol at st. michael's college school, to play hockey to pay for his education. he played three seasons of junior ice hockey with the toronto st. michael's majors in the ontario hockey association, reaching the j. ross robertson cup finals in the 1952–53 oha season. costello was signed by the chicago black hawks in 1953, and was assigned to their affiliate team, the galt black hawks, for the 1953–54 oha season. costello made his professional debut in the 1953–54 nhl season, playing 40 games with chicago. he finished the season with the hershey bears in the american hockey league, reaching the calder cup finals in the 1953–54 ahl season. he was traded to the boston bruins for frank martin, on october 4, 1954. costello played 54 games for the bruins in the 1954–55 nhl season, and 41 games in the 1955–56 nhl season, when he and lorne ferguson were traded to the detroit red wings, in exchange for real chevrefils and jerry toppazzini on january 17, 1956. after 27 games for detroit without any points, costello was sent down to the edmonton flyers early in the following season, where he finished his professional career. he played 162 games in four seasons in the nhl, and scored 13 goals, 19 assists, and 32 points. costello felt that he had the skills to play in the nhl, but not "the mindset to be an nhl player, the way they sacrificed their bodies.” costello finished his playing career with the windsor bulldogs in oha senior hockey, while he earned a bachelor of arts degree from assumption university in 1959.