Teenaged winger Braxton Sorensen-McGee snatched an intercept with 10 minutes remaining to help clinch the title.
Matatū pressed hard for a try in the dying moments and got the ball over the line several times but could not get it down.
It was heartbreaking stuff for the South Islanders, who struck first in the game.
Halfback Maia Joseph took a quick tap and Matatū charged forward.
They were stopped 5m short but swung the ball to the right.
Centre Amy du Plessis floated a long pass to Winnie Palamo and the right winger brushed off two defenders to score half a metre in from the corner flag.
The Blues were struggling to establish a foothold.
They mostly defended for the opening 10 minutes and gave up too many penalties.
The Bremner sisters, Chelsea and Alana, were influential with strong early carries for Matatū.
The pressure was mounting on the home side and eventually du Plessis got between two defenders and crashed over in the tackle.
Hannah King landed the conversion from a handy spot and the visitors led 12-0.
But some magic from Portia Woodman-Wickliffe helped swing the momentum.
She brushed off a tackle in the midfield and got the inside pass to Ruahei Demant to score.
Matatū blew the restart and gifted possession back to the Blues, who struck again.
Having got the ball into the red zone, they battered away and prop Chryss Viliko smashed through to level the scores.
The Blues went ahead with a conversion and took a two-point lead into the halftime break.
Matatū had 20 minutes of hard work wiped out in a five-minute burst.
The Blues were back on defence early in the second period but scrambled nicely.
Matatu kept the Blues pinned deep in their territory and chipped away until a crack emerged out on the right.
Powerhouse No 8 Kaipo Olsen-Baker busted through from close range.
The 19-14 lead was short-lived.
Demant skipped through a tackle from a 5m scrum and got a nifty offload to Woodman-Wickliffe and she dotted down under the posts.
Matatū hooker Georgia Ponsonby picked up a yellow for making head-on-head contact in the 64th minute.
But the Blues’ numerical advantage did not last long.
Eloise Blackwell came on as a replacement and four minutes later was given a card for the same offence.
There was no mitigation this time and it was ruled a red card.
But the game was decided by one loose pass from Palamo.
It was intercepted by 18-year-old Sorensen-McGee and she scampered 70m to score.
Aupiki final
The scores
Blues 26
Ruahei Demant, Chryss Viliko, Portia Woodman-Wickliffe, Braxton Sorensen-McGee tries; Krysten Contrell 3 con.
Matatū 19
Winnie Palamo, Amy du Plessis, Kaipo Olsen-Baker tries; Hannah King 2 con.
Halftime: Blues 14-12.
