Ponga is set to make his Kiwis debut at this year's World Cup after writing to the IRL and having his application unanimously approved at Wednesday night's board meeting.
The WA-born fullback had been eligible to represent either the Kangaroos or New Zealand, where his parents were born, but aligned with Australia in 2018 by making his State of Origin debut.
But a 2019 nines tournament and caps for the Junior Kangaroos marked Ponga's only appearances for Australia, giving the Newcastle star a strong case as he appealed to the IRL to approve his switch.
"These were appearances I am grateful for; however, upon reflection, they do not reflect where my heart, my heritage, and my deepest sense of belonging truly lie," Ponga wrote in his application.
"While I was born in Australia, my connection to New Zealand runs deep through every generation of my family.
"My roots, my whakapapa, and my identity are firmly grounded in
this country and its people."
Ponga has previously made three appearances for the Mãori All Stars in the annual fixture against the Indigenous All Stars.
"Those experiences have only deepened my connection to New Zealand rugby league and to the broader Mãori community," Ponga wrote.
"I am immensely proud of my Mãori heritage, and that pride has oniy grown stronger with each passing year."
The acquisition of Ponga is a boost to New Zealand's hopes of a first World Cup title since 2008.
He will join James Fisher-Harris, Leo Thompson and Knights teammate Dylan Brown among high-profile Kiwis in selection consideration.
The switch also means Ponga will never represent the Kangaroos, with tier-one eligibility changes considered final by the IRL.
Flipping allegiances to New Zealand would previously have meant 10-time Queensland representative Ponga turning his back on State of Origin.
But as of mid-February, New Zealand and England internationals are able to play Origin provided they were born in NSW or Queensland, their father played Origin or they resided in either state prior to their 13th birthday.
Ponga lived in Queensland during his youth so he remains eligible.
