The Chiefs held on to topple Super Rugby playoff masters the Crusaders 20-17 in Hamilton on Friday night to book a place in just their second final.
A brutal, nerve-jangling semi-final at Waikato Stadium was won by a more desperate Chiefs side, who harried their fancied rivals into mistakes while scoring two tries to one.
They held onto a three-point lead over the final quarter and a capacity crowd of 25,000 heaved a sigh of relief when Crusaders five-eighth Dan Carter missed a chance to send the game into extra time with a stray long-range penalty.
Sonny Bill Williams, playing against his former team, showed what a loss he will be to New Zealand rugby.
His display of power running was a standout while the Chiefs pack stood strong in some brutal exchanges up front after being eclipsed when the teams last met three weeks ago.
They were stinging in defence, an area where the Crusaders were unusually poor, failing to handle the bursts of Williams and slick five-eighth Aaron Cruden.
Cruden and Carter traded early penalties before prop Sona Taumalolo gave the Chiefs a lead in the 26th minute that they weren't to relinquish, burrowing over in typical style for his ninth try of the campaign.
Flanker Liam Messam was the recipient of a super Williams offload to storm over soon afterwards and it took a try to centre Ryan Crotty on the stroke of halftime to keep the visitors in the game at 17-11 down.
Carter's two penalties after the break pulled them closer while Cruden slotted a lone penalty in the second spell.
It was just the third appearance in a semi-final for the Chiefs, compared to the 14th for the Crusaders.
The Crusaders have reached the semi-finals for four straight years but failed to add to their seven championships.
The Chiefs must await the outcome of the all-South African semi-final in Cape Town on Sunday morning (AEST) to learn their opposition and venue for next weekend's final.
They will play the top-qualifying Stormers in Cape Town or host the Sharks.
CHIEFS 20 (Liam Messam, Sona Taumalolo tries Aaron Cruden 2 cons 2 pens) bt CRUSADERS 17 (Ryan Crotty try Daniel Carter 4 pens) at Waikato Stadium. Referee: Craig Joubert.