Members of the public lined the streets and joined in songs and cheering with the demonstrators as they were arrested one by one and taken to Wellington Police Station.
Some sobbed as they were loaded into a nearby paddy wagon.
Protest spokesman Adam Craigie said 26 protesters, including spokeswoman Lizzie Sullivan, had been arrested for trespassing.
He was unsure if any charges would be laid.He said the group's "peacekeepers" were now waiting for protesters to arrive at the police station, where they would offer support.
The group wore white vests saying "Show Us Ya Text" and carried signs saying "think of our future", "why the secrecy John?" and "secret treaties are not democracy".
Earlier today, before her arrest, Ms Sullivan said the protesters were an ordinary group of Kiwis who were concerned about the closed-door negotiations.
"We've asked the Government multiple times to release the [TPP] text and they've refused so we've come up here to liberate it for all of New Zealand."
Ms Sullivan said the TPP was the biggest trade agreement New Zealand had ever signed, and wanted the text to be open to public consultation.
"We're afraid. We want to see it for ourselves.
"It seems odd they don't want us to see it. Maybe it's not in our best interests and that's why they don't want us to see it.
"We're imploring the police to let us into the building and let us see it for ourselves."
All protesters had undergone practical training in non-violent civil disobedience, Ms Sullivan said.
Mr Craigie said shrouding negotiations in secrecy was an "insult" to the intelligence of the thousands of Kiwis who protested against negotiations in August.
Thousands gathered in main cities across the country to protest against the TPP deal last month.
"We find it offensive. The Government has said we need to respect the confidentiality of the negotiation process. We believe the Government needs to respect the intelligence and judgement of the public.
"We hope that no matter what happens today that the Government will listen to reason and release the document."
The group had informed police of their plans today, Mr Craigie said.
"We apologise if we have caused any inconvenience to the public of Wellington. We just felt it was really important to come here today and stand up for the key principals of democracy, which the Government has not."