Green Island just squeezed home over North East Valley in a high-scoring affair, while Taieri had a convincing won over Kaikorai.
Taieri batted first at Brooklands and racked up 274 for nine wickets in its 50 overs.
Beckham Wheeler-Greenall scored 71 and Callum Egan hit a breezy 64, off just 36 balls.
Cam Jackson also chimed in with 40.
Matt Hunter was the best bowler for Kaikorai with three wickets.
In reply, Kaikorai scored only 154, Mitch Renwick making 30. Kaikorai lost wickets regularly and could not get a partnership going.
Ben Lockrose took three wickets for 31 for Taieri and Regan Flaws took four wickets for 29 to help Taieri to a 120-run win.
In the other match, Green Island batted first and made 265, all out with three balls left in the innings. Ant Harris scored 81 while Brad Kneebone, Gregor Croudis and Mark Joyce also chipped in with 40s.
Travis Muller was a constant threat for North East Valley and picked up a five-wicket bag.
North East Valley started out all right and Hunter Kindley made 81 but it got behind the run rate. Muller chimed in with 44 but when he was ninth man out, the target got too steep and North East Valley ended up on 258 for nine wickets, giving Green Island a seven-run win.
The final is due to be played on Waitangi Day at a venue yet to be decided.
The winner goes through to the national club one-day tournament in Auckland at the end of the season.
