Two northbound lanes on the bridge were closed earlier this morning to allow the Hīkoi mō Te Tiriti to travel by foot into the city.
Greenpeace Aotearoa drone footage shows protesters crossing in large groups with many holding flags and some stopping to wave them over the side of the bridge.
Traffic can be seen crawling alongside the crowd as people exit the bridge.
Police estimated 5000 people made their way across, starting from 9.30am, with lanes reopening to traffic about midday, while Fanshawe St reopened about 11.30am.
“We would like to thank motorists for their co-operation so far today,” police said in a statement, adding that they were continuing to monitor the hīkoi as it moved through the city.
Another questioned why police were allowing protesters to march across the Harbour Bridge during rush hour, saying authorities were “failing the vast majority of the public” to accommodate a group of “disaffected” demonstrators.
Others honked in support, eliciting waves and cheers from the protesters.
The protesters will make their way down the North Island in the coming days, protesting Government policies affecting Māori – including the contentious Treaty Principles Bill.
They are expected to reach Hawke’s Bay by Friday, Palmerston North by Sunday, then on to Porirua before arriving in the capital on Tuesday.
The Treaty Principles Bill, advocated for by the Act Party, seeks to clarify the principles of the Treaty.
While National opposed the policy during the election campaign, the party agreed during coalition negotiations to support the legislation to a select committee. Luxon has said National will not back the bill past its first reading.