"This election is going to come down to the wire and every single vote is going to count."
She told the supporters to talk to their friends and colleagues to make sure they were enrolled.
Her campaign has been pitched firmly at the younger generation - but enrolment numbers are lagging behind previous elections.
Otherwise it was her usual campaign pitch, complete with quotes from Norm Kirk and Peter Fraser, much use of words such as "hope" and a promise to solve problems from homelessness to climate change, from clean rivers to affordable housing.
She said that in some ways New Zealand was considered the envy of the world because of its economic growth. However, her measure would be how people in towns such as Ngaruawahia were feeling rather than overseas economists.
"A successful economy is one that serves its people, not the other way round. I want economic success to feel real, but it won't feel like anything but faint praise until it feels real for everyone."
Ardern said she was "back in my own backyard" and referred to her birth and early years in Dinsdale and upbringing in Morrinsville. She said she recalled "many hours doing laps down Victoria St in my friend's car, because that's what bogans did".
Afterwards Ardern took another trick from former Prime Minister John Key's book - promising to attend Waitangi Day celebrations at Te Tii Marae after her rival Bill English said he would not go back.
In 2008, Key made the same pledge after former Helen Clark said she would not return following a series of soured welcomes. Key kept that pledge until 2016, when he too pulled out. Last week, Ardern had copied Key's pledge to resign rather than lift the superannuation age.
The rally opened with Anika Moa, introduced by Tamati Coffey as the third most popular lesbian in New Zealand - after the Topp Twins.
Moa jokingly took exception, saying she liked to think she was the hottest: "They've had their time."
Moa is the latest of a string of New Zealand musicians to appear at Labour campaign events - the campaign launch featured Hollie Smith and a speech by Don McGlashan.