Cheevers' professional hockey career began in 1956 at the age of 16 when he played for the St. Michael's Majors of the Ontario Hockey Association . He was owned by the Toronto Maple Leafs until the Boston Bruins drafted him in 1965. He spent six years in all in the minors until, by 1967 , he was the team's number one goalie. He was a member of both the 1970 and 1972 Stanley Cup winning teams, gaining a reputation as a driven, "money" goaltender.
Cheevers' unusual stitch-pattern goaltender mask came after he had been struck on it by a puck hard enough to have caused him injury if he had not been wearing one, and he had the team trainer paint on the mask the stitches he would have otherwise received. Ever after, any time he was similarly struck, he would have a new stitch-mark painted on. The mask became one of the most recognized of the era, and is now in the Hockey Hall of Fame .
In the fall of 1972, he jumped to the fledgling World Hockey Association , playing three and a half seasons for the Cleveland Crusaders as one of the league's best goalies, winning First Team All-Star honors in 1973 and Second Team honors in 1974 and 1975.
Returning to the Bruins during the 1976 season after financial disputes with Cleveland management, Cheevers finished out his playing career at the end of the 1980 season. After hanging up his pads, he became the Bruins' coach, a position he held for four and a half seasons.
Cheevers was not afraid to stray from the crease both to cut down the shooter's angle and to act as a "third defenseman". He was very aggressive with opposing players who strayed into or near the crease. Not a "stand-up" goalie, Cheevers could often be found on his knees or even his side. His famous trademark was the stitches that he painted on his mask each time he stopped a puck with his face.
His cumulative NHL goals against average was 2.89. He recorded 230 NHL wins, played in 419 NHL games, and recorded 26 NHL shutouts. He was also second in the WHA's history in career GAA and shutouts, despite playing in only half the league's seasons.