He played in the National Hockey League (NHL) for the Minnesota North Stars and Detroit Red Wings, but most notably for the Boston Bruins.

In net for the Minnesota North Stars, he surrendered Jean Beliveau's 500th career goal on February 11, 1971.

[2] 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.

[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.