It peaked on Monday night with 245,000 viewers, and its Thursday night finale had 227,000 viewers aged 5+, TVNZ said.
The network also boasted the show had more than 4000 people streaming the show via its On Demand platform on Monday and Tuesday, and said more than 13,000 tuned in for a think tank livestreamed on Facebook on Wednesday night.
It also had 210,000 responses to the questions posed to viewers throughout the series.
But a spokesperson for TVNZ wouldn't confirm whether What Next? would get a second season.
It said it "certainly isn't closing the door on the future now that we've thrown it wide open".
"We are delighted with the show ... it succeeded in that it truly set the ball rolling - getting New Zealanders involved, not only thinking and talking about their futures but ideally motivated into action to steer their lives towards the future they want for them and their children and families."
A NZ on Air spokesperson said it was happy with the show's "strong" audience and its $1,219,288 investment.
"It had highly active and positive audience participation from all over NZ which is no mean feat," said a spokesperson.
"What Next? was a ground-breaking multimedia event and we are very happy with how it grew and developed over the five nights."