New Zealand will have been optimistic they could end their run of defeats after triggering a collapse of 7-28 to bowl the hosts out for 142 in the 20th over in Mackay on Sunday night.
But the visitors could only muster 7-113 from their 20 overs, unable to move up the gears after a steady, wicketless first six overs of their chase.
The 29-run victory followed the world champions' comfortable five-wicket win in the first game on Thursday.
Gardner also made a handy 18 runs before becoming one of Amelia Kerr's four scalps. (Darren England/AAP PHOTOS)
Ashleigh Gardner (3-16 from four overs) enjoyed a successful return after she missed the series-opening win, while captain Alyssa Healy's (38 off 25) bright start proved decisive.
Amelia Kerr's career-best spell (4-20) had given New Zealand hope after Healy and Ellyse Perry (34 off 33) looked comfortable, the spinner knocking over Gardner then taking three wickets in her final over.
Phoebe Litchfield and Sophie Molineux took sharp catches to dismiss key pair Suzie Bates (34 off 34) and Sophie Devin (four off 10) and send Australia towards victory.
There were fumbles though. Megan Schutt dropped a sitter at point late in the game, while several run-outs went begging.
Perry's dismissal was also forgettable, the allrounder taking off for a run after being struck on the toe, only for the wicketkeeper to whip off the bails.
When you accidentally press the triangle button 😬 😬 😬 — cricket.com.au (@cricketcomau) #AUSvNZ pic.twitter.com/yjhc0qnCNnSeptember 22, 2024
The sides will complete their series at Brisbane's Allan Border Field on Tuesday before departing for next month's World Cup in the UAE.
"Probably not the prettiest, but those are pretty important wins to prepare us for what's to come," Australian allrounder Annabel Sutherland said.
"I'm pretty proud of the group; the way they stuck together with the ball and found a way to win pretty comfortably in the end.
"We didn't quite get the total we were after but ... a win's a win."
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