Both sides were unbeaten going into Sunday's (Monday AEDT) decider after perfect pool action and semi-final wins, where the Aussies defeated Fiji 22-14 to set up a grandstand end to the tournament against their fierce trans-Tasman rivals.
First-half tries to Maddison Levi and a double from sister Teagan had Australia up 21-5 at the break, after trailing to a second-minute Kelsey Teneti five-pointer.
Australia and New Zealand have contested all six finals this season, with the Kiwis winning five, and Tim Walsh's side couldn't hang on in New Jersey, conceding tries in the 10th, 12th and 14th minutes.
The Black Ferns had already won the series title when they qualified for the semis, but still wanted to finish the regular season with a win and did so in remarkable circumstances.
"I think for us, even before the game started, we knew it was all going to be about heart," NZ captain Risi Pouri-Lane said.
"Final footy can go either way and we all know that. But to grind it out when the odds may not be in your favour is what counts."
South Africa beat Fiji 10-7 in the men's decider to also claim the series crown, while the Aussies finished fourth in the US after losing 28-7 to the Pacific Islanders and then 26-10 to Argentina.
New Zealand's women and South Africa's men also triumphed a week ago in Vancouver.
The Blitzboks led through Selvyn Davids and Tristan Leyds increased their lead two minutes into the second half, before Fiji rallied with a try to Terio Veilawa with two minutes remaining.
"It was just a massive, massive defensive effort," South Africa captain Impi Visser, who played his 50th World Series match in the final, said.
"Fiji brought out the best in us. It's funny that it all came down to the final ... It's like someone scripted it, and couldn't have scripted it better."
With AP.
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