The 1919-20 Thunder Bay Senior Playoffs were won by the Fort William Maple Leafs. They defeated Alberta champion, the Lethbridge Vets in the semi-finals after Lethbridge conceded the two game total goals series after losing the first game 15 to 2. They lost to eventual Allan Cup and Olympic gold medalists, the Winnipeg Falcons in the final round.
No further information is available on the actual district playoffs.