She helped behind the barbecue with Green Party co-leader James Shaw and other MPs as 1000 people waited in line for breakfast.
She started the tradition in 2018 which replaced the more formal Prime Minister's breakfast held at the Copthorne Hotel which was closed off to the public.
Earlier, about 500 people gathered at Te Whare Rūnanga - the carved meeting house at the Upper Treaty Grounds, for the annual dawn ceremony which marks the start of Waitangi Day.
There was a moment of quiet before thousands of people descended on the small Northland town to enjoy a day of whānau fun.
Ihumātao protesters are among the crowd, although have been peaceful.
Waitangi National Trust Board chairman Pita Tipene welcomed the crowd. He said it was an honour and privilege to have everybody there.
At the start of the service, the Leader of the Opposition Simon Bridges was announced as second speaker after the Prime Minister, but he left yesterday morning. Alfred Ngaro will speak in his place.
Ardern started with a prayer.
"Today we pray for our people, our history and our future. On this 180th Waitangi Day let us pledge to take a step across the bridge between our peoples.
"Give us the perseverance in our daily lives to commit to a simple action that helps take us to the other side. And in doing so, give us the courage to learn to walk comfortably in each others' shoes.
"God we also pray for those in need, the poor, the sick, those who suffer prejudice and the lonely. Make us better people who look after all our brothers and sisters.
"At this place, on this day, may we unite in kindness and care towards one another."
She ended her address by reading the second verse of the national anthem.
Last week, the Weekend Herald revealed she had told a Hobsonville resident the anthem's "language is certainly a product of its time", and advised that change "could evolve if enough people supported it".
Fiona Downes wrote in a letter to the PM that she believed more people would be able to relate to "the simple and direct words of the second verse".
Act leader David Seymour said "there is nothing like Waitangi Day anywhere, part ceremony, part conversation" and it "makes me proud to be a Kiwi".
He also joked that it's "sometimes rambunctious but you have to forgive the politicians".
Race Relations Commissioner Meng Foon, invited to speak in "any language he likes", spoke in Māori, Chinese and English and called on everyone to show love for each other.
Tipene - who has played a key role in Ngāpuhi's Treaty Settlement process - said people were using te reo more in conversation.