Born in Lindsay, Ontario, Maloney was a junior standout with the OHA's Kitchener Rangers. After scoring 104 points for the club in 1977-78, he was claimed 26th overall by the New York Rangers at the Amateur Draft. He adjusted quickly to the pros by recording 44 points in 38 games for the AHL's New Haven Nighthawks. Partway through the season, Maloney was recalled to Manhattan and averaged nearly a point per game in 28 matches. He also led all playoff performers with 13 assists while joining his brother, Dave, in helping the Rangers reach the Stanley Cup finals.

Beginning in 1979-80, Maloney registered five straight 20-goal seasons in New York. He often worked well with linemates Phil Esposito and Dean Talafous and notched a personal-high 29-goal season in 1980-81 and 1982-83. The crafty forward also took part in the 1983 and 1984 NHL All-Star Games, winning the MVP award at the latter at the Meadowlands Arena. After an injury-plagued season in 1984-85, the classy veteran helped Canada win the silver medal at the World Championships. The next year, he rebounded with an outstanding defensive performance and helped the Rangers reach the Prince of Wales Conference finals.

Late in his career, the Rangers decided to make changes and sent Maloney to the Hartford Whalers. He played the last 21 games of the 1988-89 season and the first round playoff loss to the Montreal Canadiens before signing with the New York Islanders as a free agent. Maloney scored 16 goals and provided leadership and playmaking savvy to the young squad before retiring in 1990-91.

Prior to the 1992-93 season, Maloney took over as the Islanders' general manager from the legendary Bill Torrey. He remained in that capacity until Mike Milbury replaced him in 1995-96. The high point of Maloney's tenure on Long Island was the club's upset of the defending Stanley Cup champion Pittsburgh Penguins while marching to the semi-finals in 1993.