He was drafted 1st, 19th overall, by the Colorado Rockies in the 1980 NHL Entry Draft from the junior Windsor Spitfires. Gagne played two seasons for the Rockies and 4 years with the relocated New Jersey Devils. Despite good numbers by him, the teams were terrible and Gagne never played a single playoff game. He injured his back in 1986 and took two years off, working in the Devils' front office. He tried a comeback with the Toronto Maple Leafs in 1988-89. But that and a try with the New York Islanders the next season were unsuccesful.