Otago will play North Harbour for a chance for either side to get into the Premiership for the first time.
The Blue and Golds bagged a home final on Friday night when they beat Bay of Plenty 27-20 at Forsyth Barr Stadium, and North Harbour then won the semifinal against Wellington in the capital on Saturday.
North Harbour went into the match as the clear underdog.
Wellington was full of Super rugby players and had finished just behind Otago on the competition ladder after the regular season.
But North Harbour was abrasive and tough throughout the match and led 20-18 at halftime before running out a 40-37 winner.
Bryn Gatland scored a penalty with under five minutes left to give his side a 10-point lead before Wellington scored a try right at the death.
New Highlanders winger Tevita Li had a stand-out match and will have to be watched carefully on Friday night.
North Harbour has been on a good run over the past few games, following a few years of struggles, winning just four games in three seasons at one stage.
But under coach Steve Jackson, who is off to assist the Blues at the end of the season, the side has turned it round and is now into its first final since the days of Frank Bunce and Walter Little.
Otago should have a fully fit side to pick from and has the huge incentive of getting into the premiership for the first time since the competition was split into two divisions in 2011.
Otago has not lost to North Harbour since 2010 and beat it earlier this season, 24-13 at Forsyth Barr Stadium.
The Premiership final will be played between Canterbury and Tasman in Christchurch on Saturday night.
In New Plymouth, Tasman beat Taranaki 41-29 while in Christchurch, Canterbury beat Counties-Manukau 22-7 in the early semifinal.
