The party's annual conference is being held in Dunedin for the first time since 1988.
After welcomes from party president Nigel Haworth and a civic welcome from Mayor Dave Cull, Ms Ardern told delegates they would hear her repeat two things a lot over the weekend - "thanks" and "we've got so much more to do".
She reeled off a long list of reforms her Government has enacted in its first year in office - "I'm very proud of that
list, but also a little bit exhausted by it as well."
She then challenged delegates to devote the weekend to achieving further changes to better New Zealand.
"There is much more to do to make our economy more sustainable and to better spread prosperity to all."
Earlier in the day, after touring AD Instruments' warehouse precinct head office, Ms Ardern said speaking to Labour Party faithful for the first time as Prime Minister would be a moment for reflection.
"I didn't expect, the last time I spoke to a Labour conference, to be in the position that I am in," she said.
"It will be a chance for reflection and to lay out some of the things we want to tackle going forward."
As a long-time Labour member, Ms Ardern said she had seen party conferences in both opposition and government, and in both cases the membership had been "free-speaking".
"We constantly push each other to make sure we use the time we have in office wisely.'
Ms Ardern said she did not want to give too much away as to the content of her leader's speech at the Dunedin Town Hall tomorrow afternoon, and would not be drawn when asked if there would be any major announcements.
"The tone of it will be future-focused, talking about all the opportunities we have to change things for future generations."
Today, the main speakers will be Ms Ardern's deputy, Kelvin Davis, and Finance Minister Grant Robertson.
The Prime Minister will also host a young leaders' panel.
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Comments
"....for their efforts in winning the 2017 election."
But they (Labour) didn't win; National did.
And as one Aussie newspaper printed: "The losers have become the winners!"
Yes, I'm aware of Winston and know about coalitions, but personally I just think there's something obscene about the party getting the most votes being shut out of power. Moreover, thank goodness my neighbour to the south still has the FPTP system or we in Canada would have had Hillary "what does it matter" Clinton to deal with.
Well thank goodness we are not still stuck in the 70 s mentality here down under and have moved forwards .