The gathering is said to be the largest since the foreshore and seabed protests in 2004.
The organisers of today's climate strike claim 170,000 people have participated in demonstrations nationwide.
Armed with placards and chants, the group of mainly students called on the Government to fight climate change.
Thousands protesting climate change down Auckland's Queen street
#climatestrike #FOCUSLIVE
Posted by nzherald.co.nz on Thursday, 26 September 2019
There were at least 5000 "strikers" massing outside Parliament – so many in fact that they poured out on to the nearby streets.
The size of the gatherings across the country have drawn the attention of Thunberg, who has been tweeting about them.
The mass strike took place despite warnings not to miss school by Acting Prime Minister Winston Peters.
On Tuesday, he said anyone planning on marching in the protests today should stay in school because they would be able to learn all they need to know about climate change by "seeing what the Government is doing".
"I support people going to school and getting the greatest education they can, as fast as they can to lift our educational standards because it's one of the critical components of lifting massively this country's productivity," he told RNZ.
But asked if school kids should be striking, Education Minister Chris Hipkins said that it was a matter for their parents and schools.
He said there was a lot they could learn through civic activity, such as the climate strikes – "so I'm not going to condemn them for that".
"I want kids in school learning and if they're not in school learning, then I want to make sure what they're doing is contributing to their learning."
If they are learning through the strikes, Hipkins said that was a good thing.
Addressing the crowd, school students implored law-makers to do more when it comes to climate change.
They want Parliament to declare a climate emergency.
Climate Change Minister James Shaw – who was at the protest at Parliament today – said it was "staggering" to see so many people.
In fact, he said today's crowd rivalled the size of the foreshore and seabed protests in 2004 – one of the biggest protests in New Zealand's history.
Shaw said the size of the gathering shows the extent to which people are worried about climate change.
Asked by climate change protest organisers if they support a stronger Zero Carbon Act than the one currently going through Parliament, Shaw said "you bet".
He passed the microphone to National's Nick Smith, who was booed before he said anything.
But he pointed out that National had supported the first reading of the bill and, when in Government, signed up to the Paris Agreement.
Meanwhile, other National MPs took to Twitter to voice their opposition to a sign that read "help farmers phase out animal farming".
Judith Collins said young people were being "brainwashed to hate farmers. Shame on this Government".
Crowds have gathered nationwide as thousands of schoolchildren combine to march against climate change.
It's the third School Strike 4 Climate, but this time organisers called on the wider public to join - dozens of businesses and organisations across the country are promising to shut their doors and take part.
An open letter with more than 11,000 signatures will be delivered to Parliament, calling for the Government to declare a climate emergency and to start building a renewable and regenerative economy.
More than 40 events are being held across the country, as part of an international movement sparked by Greta Thunberg.
It caps off a week in which the movement's 16-year-old figurehead Thunberg dressed down a summit of world leaders, and a major UN report warned time was fast running out to solve the climate crisis.
More than 40 events around New Zealand are scheduled today, from large demonstrations in main centres to rallies in places as remote as Great Barrier Island.
"We are definitely expecting it will be the biggest turnout yet," said the strike's national co-ordinator, Paekakariki teen Sophie Handford.
Last Friday, millions of young people packed out parks in world cities like Sydney, Berlin and New York, as part of the global push.
Handford said New Zealand's events had been scheduled a week later because many students were sitting school exams.
"But there happens to be a global strike on September 27 as well, involving 170 countries and more than 6300 events – so we are looking at something the same size as last week."
Today's event was organised in solidarity with Wellington protester Ollie Langridge's weekly vigil on the lawns of Parliament, calling for the Government to declare a climate change emergency.
Handford was heartened that workers from 90 businesses – ranging from bookshops and bakeries to consultancies and architecture firms – would be downing tools to take part.