Rawiri Waititi will take-over from John Tamihere as Māori Party co-leader after winning the seat of Waiariki.
The preliminary results from election night show Waititi won against Labour's Tāmati Coffey by 415 votes.
Waititi is also Tamihere's son-in-law. Tamihere was unsuccessful in his bid for the Tāmaki Makaurau seat.
"He's the spokesperson, the face of the party now, and so he will by dint of his success - and rightly so - take over the co-leadership," Tamihere told The Hui.
Tamihere added he won't be leaving the Māori Party and indicated he may stand again in the 2023 election.
Waititi's win in Waiariki has led the Māori Party to one of the most remarkable political comebacks of recent times.
A defiant Coffey is yet to concede in the seat, and said he's awaiting the special votes to be counted.
Waititi said Waiariki voters have sent a message to Labour's Māori caucus.
"We must continue to push our people into a space where our people are unapologetic about who we are [and] that we speak our indigenous truth in every space that we can engage in," he said.
The Māori Party's Debbie Ngarewa-Packer lost her bid for the seat of Te Tai Hauāuru but will stay on as co-leader. There's still a chance she may still make it to parliament on the party vote.
"This little party was at the brink of non-existence and has clawed back to have one candidate, possibly more coming through with the party vote," she told Newshub on election night.
"We just had so much not going in favour for us and yet we have proved Māori do want to have that independence, so I'm feeling fabulous."
Former National Party MP Tau Henare said the resurrection of the Māori Party was the biggest winner on election night.
"It wasn't talked out [during the mainstream media election coverage] because there's so little understanding of what Māori politics is about," he said.
"It is only one seat but that brings with it all the resources of a Member of Parliament, all the ability to get in front of the camera - it's the new beginning of the Māori Party. And let's not forget the great job every candidate did trying to claw back [the Maori seats]."
While Labour has lost Waiariki, the party's extraordinary win overall will see its Māori caucus grow to at least 15 MPs.
"It is the largest Māori caucus of any party in the history of New Zealand," Labour's deputy leader Kelvin Davis told The Hui.
"They are going to complement and build on the strengths that we already have."
Asked whether he wanted to be deputy prime minister, Davis said it's too early to discuss specific roles. However, Labour MP Peeni Henare was more forthcoming, and said: "I have got huge faith in Kelvin and I think he'll make a great deputy prime minister".
