In an important victory for the party, Mr Tirikatene (39) wrested the seat from the Maori Party's Rahui Katene by 1445 votes. Although the Maori Party was expected to be punished for its deal with National, Mrs Katene had been a strong campaigner.
"I was quietly confident all along because I knew we had put a lot of work into the campaign.
"I'm thrilled to be the new MP for Te Tai Tonga," Mr Tirikatene said.
Mr Tirikatene's family history is intertwined with the seat, which his grandfather and aunt have represented.
Labour retained its party vote majority, which was cut from 5419 to 3411, with the Greens in second place instead of the Maori Party.
On Saturday, the Maori Party was fourth in the party vote, behind National.
Mr Tirikatene, who has a background in Maori business and law, lives in Wellington but planned to shift to the South Island. He had not decided where he would be based, but Invercargill was a possibility, as he could cover the electorate from both ends.
Covering New Zealand's biggest electorate posed obvious challenges, and Mr Tirikatene wanted to have a strong physical presence, as well as making use of technology.
While he would prefer Labour to be in Government, being in opposition would give him a good grounding as a new MP, he said.
Mrs Katene could not be contacted.
