In all, the 20-strong cabinet includes eight women, five who are Maori, three who are Pasifika and three who are openly LGBT.
Importantly for Australia, Nanaia Mahuta will become foreign affairs minister - the first woman to hold the role - and Damien O'Connor will become trade minister.
Ms Ardern surprised with a significant shuffling of her ministerial pack, necessitated by the departure of first-term coalition partner New Zealand First from the incoming parliament.
Former leader Andrew Little was moved from justice to health, Poto Williams picked up police and Peeni Henare will become defence minister.
Chris Hipkins retains education and picks up a new COVID-19 response ministry.
Ms Ardern said her government would have "two overarching priorities".
"To continue our health response to keep New Zealanders safe from COVID-19, and to drive our economic recovery and ensure we take the opportunity we have in front of us to build back better," she said.
One of her first-term MPs, infectious diseases specialist Ayesha Verrall, will go straight into cabinet as Seniors minister and associate health minister.
Ms Ardern said she was "excited to be bringing in some new talent" that "reflected the New Zealand that elected us on the 17th of October".
"One of the amazing things about New Zealand, is that we are often in a space now where all of these questions often become secondary," Ms Ardern said of her diverse government.
"This is a cabinet, and an executive, that is based on merit, who also happen to be incredibly diverse and I'm proud of that."
Mr Robertson said it was a "true honour" to be given the job alongside one of his best friends.
"The relationship that I have with the Prime Minister as well now we've known each other personally for a long time, and worked together professionally for a long time as well," she said.
He batted away the suggestion her decision anointed him as New Zealand's next PM, saying "Jacinda Ardern doesn't need a successor".
Mr Davis denied being pressured not to take up the deputy PM role.
"Jacinda and Grant are the dream team. They have my 100 per cent support," Mr Davis said.
The Labour government will be supported by two Greens ministers outside cabinet; James Shaw as climate change minister and Marama Davidson as family violence minister.
The new cabinet will be sworn in on Friday after the Electoral Commission confirms the final election count, meeting for the first time later that afternoon.