In 1973-74, he was traded to the Bruins as a replacement for Gerry Cheevers who had gone to the World Hockey Association (WHA), played in the NHL All-Star Game, and helped the team to the Stanley Cup finals that year. The Bruins lost the Finals series 4-2 to the Philadelphia Flyers, but over these six games Gilbert played as brilliantly as his opposing counterpart Bernie Parent who was named playoff MVP.[3][4]
In the 1975–76 NHL season, Gilbert set the NHL record for most consecutive wins by a goaltender with 17, and finished with a 33-8-10 record for a .843 winning percentage in 55 games.[5]
From 1976 to 1980, he teamed with Gerry Cheevers to form one of the best goaltending duos in the NHL, being runners-up for the Vezina Trophy in 1980.
Gilbert recorded 17 playoff victories for Boston. As of 2019 he ranks sixth in all-time playoff wins among Boston goaltenders.
Gilbert was the Bruins goalie during the 1979 Stanley Cup playoffs semifinal game 7 against the Montreal Canadiens, when Guy Lafleur tied the game after the infamous too many men penalty against Boston, and then Yvon Lambert scored the series-winning goal in overtime; Gilbert was still named the game's first star. Cheevers was benched after losing the first two games of the series, and Gilbert took over as the starter thereafter, overall being named the game's first star three times in the five games against Montreal. Montreal's Steve Shutt exclaimed of these performances that “Gilles Gilbert stood on his head. He was the reason they got to the seventh game”.[6][7]