The number of people who say they have no religion has reached 1.6 million.
Statistics NZ has released more data from Census 2013, which shows the number of people who identify as having no religion has increased by 26 per cent since 2006.
At the same time, people affiliating with Christianity fell 8 per cent to 1.9 million.
Of the largest denominations, Catholic, Anglican and Presbyterian all decreased, while Pentecostal increased. The number of followers of Hinduism and Islam increased.
Association of Rationalists & Humanists president John Murphy said the Census result would ensure the non-religious were acknowledged and heard by society.
"It means that the people who make our laws and so forth now need to take into account the wishes of people who are not religious, because we are becoming a significant part of the population."
The group ran an advertising campaign before the Census urging people who were not religious to say so. Mr Murphy said it had become more acceptable in society not to associate with a religion.
"This helps us normalise the position of being non-religious."