"Thanks for helping to put us into Government."
She added that was still "so much work to do".
"I know that none of us take that for granted. But tonight, perhaps just tonight, before we crack into the 'what next and what more' perhaps we can quickly look at what we have been able to do so far."
She then spent a minute or two listing off the various achievements of the Government so far, ending on how they were poised to pass child poverty reduction legislation.
She and the official party were piped out of the Dunedin Town Hall into the foyer where she met up with partner Clarke Gayford carrying baby Neve.
Ardern rushed over and cupped the baby's head in her hands, indicating it was cold and put a bright red hat on her.
Auckland mayor Phil Goff was the party's first leader straight after losing Government in 2008 and he said the party was the most unified it had been "in decades".
He was attending as an observer and to network but he said the weekend would be a real celebration.
"People are delighted that Labour is back in Government but they delighted at the performance of the Prime Minister. I think she has performed superbly."
The conference would be serious because Labour conferences always were, he said.
"It's about how we can change the world and how we can do it by yesterday.
"The level of party unity is higher than you've seen in decades."
There had been enormous respect for former Prime Minister Helen Clark and her commitment "but with Jacinda you've got that respect with another dimension".
She was a new generation Prime Minister and "what you see is what you get".
Ardern's performance at the United Nations in New York had made Kiwis feel proud, Goff said, "that this was the image of New Zealand that was going out to the world".
"I am finding that just as much among people who are not Labour voters," he said.
Finance Minister Grant Robertson and deputy leader Kelvin Davis will speak tomorrow and Ardern's big speech will be on Sunday.
Earlier in the day in Dunedin, Ardern expressed concern that the Sroubek issue could linger on for another three weeks - the time Immigration Minister Iain Lees-Galloway gave for officials to report back to him.
Ardern has intervened and said she expects it to be dealt with urgency and a lot less than three weeks.