Due to injuries and with his skills not what they used to be, Clapper originally retired before the start of the 1946–47 season, but returned to play in November 1946 to replace the injured Jack Crawford in the Bruins' lineup. He played only once in awhile thereafter, and retired for good on February 12, 1947. Leading the Bruins to a 10-1 victory over the New York Rangers in his final game (in which Bill Cowley broke the league career scoring record, the Bruins further announced that day that his number #5 sweater would be retired, and the Hockey Hall of Fame immediately inducted him as an Honoured Member; he was the only active player ever to be inducted into the Hall, and at the time the only living Member inducted. 