Speaking to reporters this afternoon, Ardern said she would be sending him the same message as all his fans around the world.
"Get well soon."
She revealed the pair had briefly caught up before his show last night.
"As you could imagine, he was busy preparing for his show. But I thought it was incredibly kind of him to give some time like that, given he obviously felt incredibly unwell."
Ardern said she could tell he wasn't feeling well when she met him yesterday.
In fact, he told her as much.
Ardern said the fact he spent about two hours on stage giving such a huge performance was "incredible and very generous".
She said they had a normal discussion, briefly touching on politics.
She confirmed that the pair did not sing a duet.
"I might have commented on how Neve loves to dance to his music – just things that you would have a normal conversation about."
In the past, Sir Elton has said he is a fan of Ardern's.
During an interview with the Guardian, he described her as "one of the few politicians that I respect and love".
The answer came in response to a question about which woman alive he would want to be, if he could pick one.
"She's got dignity and she's humane," Sir Elton said.
"I think she's doing a brilliant job."
Asked about it at the time, Ardern said she was genuinely humbled and flattered and more than a little surprised.
"Because you don't often hear someone of his standing and his role wanting to be a politician."
