Ardern said the meeting at Buckingham Palace (at 3.45am NZT) was an opportunity to convey the deep sadness felt by New Zealand at the loss of Queen Elizabeth. And it was also a chance to offer condolences directly to him.
She said the King was deeply appreciative, and was moved that Kiingi Tūheitia had come to London.
Earlier, in a meeting with New Zealand Governor General Dame Cindy Kiro, King Charles spoke of his deep affection and commitment to New Zealand, and said he looked forward to visiting sometime in the future.
Ardern is scheduled to meet with other world leaders tomorrow at a reception hosted by the King for the international leaders attending the Queen's funeral.
Ardern also met new UK Prime Minister Liz Truss overnight, and the pair discussed the war in Ukraine and New Zealand's free trade agreement with the UK.
The pair met in London at 11pm Saturday NZT.
Ardern said Truss expressed gratitude at the role New Zealand had played alongside the UK, in dealing with the Ukraine war.
And that Truss was keen to see the free trade agreement brought to fruition.
It was the first time they had met in person. Truss had already met the Minister of Foreign Affairs Nanaia Mahuta and Minister of Trade Damien O'Connor.
Ardern said New Zealanders could count on an ongoing and strong relationship with the UK.
"There's a relationship there and you could sense that. New Zealand's issues - the things we're interested in, she was very familiar with."
