Following a 24-goal campaign in his final season with the Maple Leafs, Henderson officially moved to the WHA where he played in another tournament against the Soviets. While the original series was restricted to players from the NHL, the 1974 Summit Series featured a Canadian team made up of WHA players. The series lacked the intensity of the original, yet Henderson felt that he played well: he scored two goals and an assist, and though Canada finished with one win, four losses and three ties, he felt the WHA had proven itself. Henderson scored 33 goals and 63 points in the 1974–75 WHA season for the Toros while playing 58 games. He missed the playoffs after tearing his knee ligaments in a game against the Phoenix Roadrunners when colliding with Bob Mowat, an opposing player during a line change.