The area around Tory Street, between Courtenay Place and Wakefield Street, has been cordoned off.
There were no cars or people in the parking building, as it was being earthquake-strengthened after earlier damage as a result of an earthquake in 2013.
Speaking to Checkpoint with John Campbell, Mayor Justin Lester said the building was badly damaged in the 2013 quake, and engineers said today it should be closed.
He said it was likely beyond repair and would need to be taken apart and come down.
Mr Lester said scores of people had been told to evacuate.
"They've had three assessments and they've decided there's significant structural damage to the car park," he said.
"So we've decided to put a cordon around the building ... and we're asking those people that live in the precinct and around that building to come out of their premises.
"There's no choice about this, because their safety as a paramount concern here, so we've required them to come out."
Mr Lester said the cinema complex was not affected by the structural damage, but because it was right next to the car park, it would be closed.
Affected buildings in the area included Maison Cabriole Apartments, several shops in Tory Street, a Chinese restaurant and a Japanese restaurant.
Several other buildings directly adjoining the parking building were also affected.
Toby Jones, who arrived from England a few months ago, was among the dozens of people scrambling to find a place to stay after being evacuated from their homes near the carpark.
He was unable to get into his apartment and had no idea when he would be allowed back in.
The Wellington City Council said the cordons would be in place until further notice - possibly weeks.
The carparking building with scaffolding in jeopardy of collapsing. Photo: Rebekah Parsons-King
Metlink said buses were still running on the Courtenay Place route, but traffic was congested and delays were likely.
Fire Service regional commander Brendan Nally said there was a significant risk of the building collapsing toward Courtenay Place if there was another major aftershock.
"But because of the structure, it's a simple car park structure, there's no glass in it for instance, it's likely to collapse in on itself."
Mr Nally said those with cars inside the cordon would not be able to get them out at this stage.
The service has brought in 15 urban search and rescue specialists to assist the council with work relating to damaged buildings.
A centre has been opened to provide shelter for people evacuated from the area.
The Wellington Region Emergency Management Office said those evacuated were being advised to stay with friends or family for the evening if they could.
But those who had nowhere to stay could go to the emergency assistance centre at the Salvation Army on Jessie Street, where they would be helped by council staff.
Photo: Rebekha Parsons-King