The announcement came hours after the Supreme Court ruled that not allowing 16 and 17-year-olds to vote amounted to age discrimination.
But critics say lowering the voting age is an uphill task as it requires backing from 75 per cent of lawmakers.
Ms Ardern, who leads the liberal Labour Party, said she supports a decrease in the voting age.
“I personally support a decrease in the voting age but it is not a matter simply for me or even the government,” ms Ardern said. “Any change in electoral law of this nature requires 75 per cent of parliamentarians’ support.”
Ms Ardern said the vote would likely take place within the coming months but any change would not take effect until after next year’s general election.
The liberal Green Party said it supported a change.
“Young people deserve to have a say in the decisions that affect them, both now and in the future,” said Golriz Ghahraman, the party’s electoral reform spokesperson.
But New Zealand’s two main conservative opposition parties said they oppose a change.
“It’s not something we support,” Opposition Leader Christopher Luxon told reporters. “Ultimately, you’ve got to draw the line somewhere, and we’re comfortable with the line being 18.”
At the Supreme Court, four judges found in favour of the lobby group’s appeal with a fifth judge dissenting to some aspects of the decision.
In New Zealand, the protection against age discrimination begins at 16, and the judges ruled that the attorney-general had failed to show why 18 had been chosen as the age to vote rather than 16.
The nature of the court’s ruling compelled New Zealand lawmakers to at least debate the issue, but it didn’t compel them to take a vote or to make a change.
New Zealand’s voting age was previously lowered from 21 to 20 in 1969, and then to 18 in 1974.
A number of countries are debating whether to lower their voting age. Some that allow people to vote at 16 include Austria, Malta, Brazil, Cuba and Ecuador.