The charismatic 37-year-old will lead a three-pronged coalition comprising her centre-left Labour Party, the populist New Zealand First (NZF) and the Greens.
NZF leader Winston Peters and the Greens have a rocky history, which descended into name-calling earlier this year when the environmentalists said the 72-year-old's anti- immigration rhetoric was racist.
Ardern insisted today that the three groups could work together and expressed confidence in Peters, an outspoken maverick whose 40-year career has been punctuated by controversy.
"Labour has been in an agreement with NZF before... Mr Peters and New Zealand First were a party of their word, that provided stability and we delivered," she told Radio New Zealand.
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Asked if her government would complete its three-year term, she replied: "Absolutely."
Ardern, who took over the Labour leadership less than three months ago and is now set to become New Zealand's youngest leader since 1856, said she was still processing her stunning rise.
"I probably need a bit of time for quiet reflection before it all sinks in, but for now it's straight to the grindstone," she told TV3.
She said it reflected the fact that the country's voting system was mixed member proportional (MMP), not first past the post.
"Obviously I'd characterise that as unfair, this is an MMP environment," she said.
"We've formed a coalition government based on the majority of votes, based on what the majority of New Zealanders sought in this election."
Ardern said she expected to allocate ministerial portfolios and release detailed policies next week, as well as implementing a 100-day plan of high-priority reforms.
Ardern said she had a low-key celebration last night over returning Labour to power after nine years in the wilderness.
"I headed straight back to my studio apartment in Wellington and had a pot of noodles," she said.