Harbour League have earned the right to take on the Auckland Lions in the last Bartercard Cup grand final in history.
The defending champions the Lions had already qualified for the showdown at Mt Smart Stadium on September 9, earning this weekend off.
Bidding to join them were last year's beaten finalists the Canterbury Bulls and Harbour League, this year's second-placed side in the regular season.
Playing at Waitemata Park in Henderson, Harbour led just 12-10 at halftime before prevailing 28-24 in a match that was always tense.
Waitemata Park, Auckland:
Canterbury Bulls 24 (M Saunders, L Tamakaha, D Aitken, J Limmer, K Leka tries; L Boyd 2 goals).
Harbour League 28 (P Samoa 2, J Freeman, D Trott, S Taka tries; D Glasgow 4 goals).
Halftime: 12-10 Harbour.