They beat the Blues 37-29 to clinch a spot in the Super Rugby Aupiki final on April 12.
And they will play the Blues in that final regardless of what happens during the final round of games next weekend.
A home venue is still up for grabs, but the Blues have the advantage.
They host the winless Hurricanes Poua, while Matatū play the competitive Chiefs Manawa in Christchurch.
The Blues also have an extra bonus point.
But suddenly the Auckland team have to work harder to stay at the top.
The Blues were unbeaten going into the fixture and started well.
Blues midfielder Portia Woodman-Wickliffe cut through in the midfield and sprinted to the line in the opening minute.
It was all gas and the odd swerve and it equalled an explosive start for the Blues.
Matatū had a chance to reply through a penalty kick.
They fluffed it and it could not have worked out better.
The Blues failed to clear it and Matatū pounced.
They turned the ball over and prop Moomooga Palu powered her way over from close range.
Openside Lucy Jenkins extended the lead.
Maia Joseph took a quick tap and swung it wide to the loose forward who went over in the tackle.
The Blues struck back midway through the half and the game was tied up 12-12 at halftime.
The home team started the second half like they did the first, with some magic.
They swept up field and flanker Taufa Bason finished off out wide.
There was some wonderful ball movement in that play and Katelyn Vaha’akolo sucked in the final few defenders and got the offload away.
Matatū rebounded immediately.
Fia Laikong picked off a loose pass and went in under the sticks.
The Blues failed to protect the ball again and Jenkins dived over for her second.
The home team needed to score next and they did.
Bason leaped over a ruck to score and set up a potentially close finish.
But Matatū scored in the corner through fullback Kaea Nepia and added a couple of penalties to secure victory.
Super Rugby Aupiki
The scores
Matatū 37
Lucy Jenkins 2, Moomooga Palu, Fia Laikong, Kaea Nepia tries; Hannah King 3 con, 2 pen
Blues 29
Taufa Bason 2, Portia Woodman-Wickliffe, Aldora Itunu, Katelyn Vaha’akolo tries; Ruahei Demant con, Krysten Cotrell con
Halftime: 12-12.
