The rally was held to show support for the more than 35,000 people gathered at Parliament as part of the Hīkoi mō te Tiriti today.
The bill seeks to define in law the principles of the Treaty of Waitangi in government legislation and law.
It passed its first reading last week with the support of Act, National, and NZ First but was opposed by Labour, Greens, and Te Paati Maori.
The bill is due to be debated in Parliament on Thursday, before it goes to select committee.
Parliament grounds were at capacity today and police and traffic wardens had to usher new arrivals to surrounding streets.
Act leader David Seymour, the chief proponent of the Treaty Principles Bill, briefly ventured outside to the gathered crowds at about 1.20pm.
He had at least four uniformed police officers and three diplomatic protection officers with him.
He left after about five minutes.
"I felt these people have made a long journey to Parliament and we as parliamentarians should be there to hear them," Seymour told reporters afterwards.
"I have to say it was quite difficult to hear a lot of what was being said, but nonetheless I thought it was important to be out there."
Te Pāti Māori co-leader Rawiri Waititi spoke to the crowd, saying no government had the right to debate rangatiratanga.
"Thanks to Hana, the whole world is watching," he said.
"My sovereign peoples, we are here, and we’re not going anywhere.”
He implored those who whakapapa Māori to switch from the general electoral roll to the Māori one, in order to boost the potential number of Māori MPs in Parliament.
"Get on the Māori roll. We have to make this a one term government."
The Prime Minister acknowledged the depth of feeling among hīkoi participants when speaking to reporters inside Parliament, saying the size of it did not surprise him.
He had previously said he would be open to meeting with a delegation from the hīkoi, but ultimately has not done so.
National instead sent a delegation of MPs out to receive the hīkoi.
"I haven't been able to meet with hīkoi organisers today. I was open to doing so but the reality frankly is many of them are Te Pāti Māori-affiliated.
"But my message more importantly to the hīkoi in general, is that our longstanding position, as I've said from day one, is we don't support the bill and it won't be becoming law."
Luxon said he would continue to meet with iwi leaders up and down the country.
In response to calls to shorten the six-month select committee process, Luxon said it was up to the Justice Committee to decide how long it should be.
NZ First's second-ranked MP Shane Jones said the hīkoi had been an "extraordinary display, flags fluttering, banners, but by and large a peaceful crowd".
He said he was slightly surprised by the response, given the Treaty Principles Bill will not be passed, but it made clear that the government must work hard to explain it is not doing anything to invalidate Māori identity.
"I think what's happened is they've tapped into a sense of anxiety within Māoridom that their rights, identity is being imperiled.
"So we've got to work very hard to ensure them that identity is not only a personal responsibility but we're not doing anything to invalidate Māori identity."
"It's proved to be a clarion call, a rallying cry, maybe the opposition parties will try and harvest some votes - but at the end of the day it's MMP politics. David put his shingle up and now he's inseverably linked to the bill."
He says it looked to him like "a hell of a lot more than 35,000 if you want my honest views", and it was a generational moment.
"The Māori race is now very young, they didn't grow up the way we did but a lot of voting power's young power. And my message to them though is that a viral moment that goes global does not necessarily survive and if you've got any doubts about, look at Jacinda Ardern."
The crowds gathered outside Parliament began to disperse and make their way to Waitangi Park by about 3pm.
A concert will now take place at Waitangi Park and a series of food trucks will provide food and refreshments to those who attend.
Hīkoi organiser Eru Kapa Kiingi thanked those who took part in the hīkoi across the country for demonstrating a clear message of kotahitanga throughout the journey.
'The movement here is magnificent'
The hīkoi left Waitangi Park at 10am, and arrived at Parliament at about 11.30am.
They were welcomed by mana whenua Kura Moeahu of Te Āti Awa, Taranaki –Tuturu, Ngāti Mutunga, Ngāti Tama, Ngāti Toa at about noon.
