A New York City native, Mullen is still one of the top five scorers in BC Hockey history.
He notched 110 goals and 212 points in his four seasons in Chestnut Hill, and was a two-time All-America, All-New England and All-East selection who led the Eagles to both the 1978 ECAC Championship and a berth in that year's NCAA title game.
He passed up an opportunity to skate for the 1980 U.S. Olympic Team, instead signing with the St. Louis Blues in order to support his family. After three seasons with Salt Lake of the Central Hockey League, where he scored a total of 120 goals, he made his NHL regular-season debut with the Blues in 1981-82, scoring 25 goals in 45 games.He later notched back-to-back 40-goal campaigns with the Blues, before he was traded to Calgary in 1985.
Mullen helped the Flames to the Stanley Cup Finals the next season, scoring 12 goals in 21 playoff games. Three years later he guided Calgary to its first Cup crown following a career-high 51 goals and 59 assists for 110 points, plus 16 more goals in the playoffs.
He joined Pittsburgh in 1990 and won back-to-back Cups with the Penguins, tallying 42 goals his second season before registering back-to-back 30-goal campaigns.
He went on to play one season with Boston before retiring as a Penguin following the 1996-97 season, a year in which he scored his 500th career NHL goal.
Mullen completed his career with 1,063 points in 1,062 NHL regular-season games, including 502 goals. In all, he recorded nine NHL seasons of at least 20 goals. He also scored 60 goals and collected 106 points in 143 Stanley Cup Playoff outings.
A three-time NHL All-Star Game participant, and an NHL First Team All-Star in 1989, Mullen was a two-time winner of the Lady Byng Trophy for playing ability combined with gentlemanly play, and also won the Lester Patrick Trophy in 1995.
He was inducted into both the Hockey Hall of Fame and the U.S. Hockey Hall of Fame in 2000, one year after BC retired his jersey.