The New Zealand prime minister is in London for the Queen's funeral on Monday night (AEST).
In media engagements while in the UK, she has been peppered with questions on the future of New Zealand's standing in the Commonwealth.
Ms Ardern's long-held position is that she believes New Zealand will become a republic within her lifetime but she will not take steps towards it as prime minister.
"There will continue to be an evolution in our relationship," she told the BBC.
"I don't believe it will be quick or soon ... because we have complex arrangements. The Treaty of Waitangi, a very important founding document for Aotearoa New Zealand, signed between Maori and the Crown.
"This is why it's not a process I have any intent of instigating, but if and when it does occur, it will take time and it will need to be very carefully worked through."
Ms Ardern has met with King Charles twice this weekend, including a one-on-one when she said she did not raise the matter.
"As you can imagine it's not the kind of conversation that in the wake of the loss of one's mother (that) you would naturally traverse," she told Today FM.
"At the same time, I've always sensed an awareness from the Royal family of the evolution of relationships, they don't stand still."
King Charles III last visited New Zealand in 2019, delivering a speech at Waitangi where he spoke kindly of Kiwis' ability to "face up to the most painful periods of her past in a way that offers an example to the world".
Ms Ardern said the King's nuanced understanding of New Zealand would ensure Kiwis take to their new monarch.
"He shares many passions and interests that New Zealanders do," Ms Ardern said.
"A relationship already exists. It's a transition, but it's not a jarring transition for New Zealand."
Ms Ardern first met Queen Elizabeth as New Zealand's prime minister when pregnant with her daughter Neve, and asked her for advice.
"I have such respect for her because I see now what it takes to be a mum and a leader and she did it more times over than I," Ms Ardern told the BBC.
"And so I said to her, 'how did you? How did you manage?' I remember she just said, 'Well, you just get on with it'.
"That was actually probably the best and most factual advice I could have. You do, you just take every day as it comes. And she did."
"The minute's silence is a way for people, wherever they might be in New Zealand, to stand together to mark an extraordinary 70 years of service," Ms Ardern said.
Ms Ardern visited the Queen lying in state over the weekend, and as a visiting dignitary, was allowed to skip the eight-kilometre long queue.
She said if she was a private citizen, she would have undergone the long wait to pay respects.
"In part as a way of acknowledging the moment in time as well as the person," she said.
New Zealand will hold a national minute's silence at 2pm on Monday, September 26, a one-off public holiday when a state memorial service for Queen Elizabeth II will be staged.
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