Australia has recorded a second consecutive defeat in the Constellation Cup, with New Zealand triumphing 52-48 in Tauranga.
The Diamonds held one-point leads at quarter-time and half-time, before the Silver Ferns took control of the match in the third term.
The home side led 39-34 at the final break, before doing enough to keep their noses in front in the fourth quarter.
The Silver Ferns won the series opener in Auckland 56-48.
The Constellation Cup moves to Australia, with the final two Tests to be played in Melbourne (Wednesday) and Gold Coast (Sunday).
The Diamonds must now win both home games and overturn their goal deficit to regain the trophy.
Away from the court, the Diamonds have other issues to resolve, including player unrest in response to Netball Australia's new sponsor, Gina Rinehart's mining behemoth Hancock Prospecting.
The Silver Ferns' victory was largely built on a flawless shooting performance from Grace Nweke, who shot 37 of 37 against the Commonwealth Games gold medallists.
On Sunday, the Diamonds were bright and attentive from the first pass, thanks in part to an improved shooting effort from Steph Wood.
The goal attack only shot at 68 per cent in game one but was superb under the net in Tauranga, shooting 21 from 23.
A super Liz Watson intercept from the centre pass helped give the Diamonds an early break, grabbing the lead from 9-9 through to their half-time advantage of 25-24.
However, the Silver Ferns lifted in the final two quarters, with Nweke and captain Ameliaranne Ekenasio both outstanding for the world champions.
Nweke's success owed plenty to the Silver Ferns' midcourt, with wing attack Peta Toeava laying of a game-high 27 assists.
"We've always been strong about finishing well against Aussie," Ekenasio said.
"We really trusted what we had in the bank tonight. We knew what we had to do … it just took us a little while to find the ability."
Diamonds coach Stacey Marinkovich offered first caps to Sophie Dwyer, Maddy Proud and Ruby Bakewell-Doran in Tauranga.
AAP/ABC
