"It's great honour for our hapu but it is definitely not to take the light away from Kelvin Davis and our other Ngati Manu MPs," she said.
The sound of warriors during the taki (challenge) echoed through the usually quiet settlement near Kawakawa.
Three warriors each laid down rau (a symbol of peace) during the challenge. The first was accepted by Mr Little, the second by Mr Shaw, and the third by Mr Davis.
Hundreds of people attended the celebration. Cars filled the fields in front of the marae, across the road, and along the street.
Sonny Tangira, who is also of Ngati Manu descent, attended the event with his mokopuna Sonny Tangira jnr.
"It's beautiful to have her (Ms Ardern) here. It is a real eye opener," he said.
The marae last hosted a Prime Minister in 2008 when Helen Clark went there instead of Te Tii Marae on February 5. That was to officially mark the selection of Mr Davis as a Labour Party candidate.
Ms Ardern promised Karetu Marae she will return, saying for her "no marae is too small".
She said it was when she was welcomed on to the marae that she felt the weight of expectation on her in her role. She spoke of the need to face up to challenges.
"If you ask me that is what Waitangi is for."
She said Waitangi should not just be about warm words and urged the speakers to continue to challenge her and her Government.
"There will be no marae too small for this Government."
Mr Davis acknowledged the tribute Karetu Marae paid him.
The event was supposed to be surprise. However Mr Davis said "well this is a surprise," adding "as much of a surprise as an open invitation on Facebook can be."