The country's largest city Auckland will go into a seven-day lockdown after a 58-year-old male from the area tested positive for what is feared to be the Delta variant this week.
The coastal town of Coromandel, where the man visited, will also go into a full lockdown for seven days. Prime minister Jacina Ardern said it was not a matter of if but when the variant arrived in the community and warned New Zealanders that Delta was a "game changer".
Officials said they could not immediately find a connection between the man and the handful of people who have tested positive while isolating in quarantine after arriving from abroad. The border is seen as the most likely source of any outbreaks. Speaking at a news conference on Tuesday, Ms Arden urged New Zealanders to wear face coverings, although it is not yet mandatory in the country.
People must stay at home in level 4, only leaving for essential services, she said. "And if you undertake these activities, please wear a mask when you leave your house."
New Zealand's vaccine programme will also be suspended for the duration of the lockdown.
Jacinda Arden promised to get tough on Delta.
"Going hard and early has worked for us before, while we know that Delta is a more dangerous enemy to combat the same actions that overcame the virus last year can be applied to beat it again," she said.
The public can drive locally to essential services, such as the supermarket.
"Remember to always act like you have Covid-19. Stay clear of others and don't put them in harm's way," Ardern said.
Ms Ardern has been promising a tough approach, including possible lockdowns, for any outbreaks of the delta variant as New Zealand continues to pursue a zero-tolerance approach toward the virus.
The last community outbreak was in February and New Zealand has reported just 26 virus deaths since the pandemic began, and roughly 2,500 confirmed cases.
New Zealand had successfully stamped out community spread, and many people elsewhere in the world looked on in envy as New Zealanders went back to work and began attending concerts and sporting events without the need to wear masks or take other precautions.However, their success in containing the outbreaks has led to a level of complacency to vaccinating their populations.
Around 25.5% of New Zealand's population has been fully vaccinated, while the figure is less than 12% in Australia.