Firefighters have now extinguished the blaze after the building site in Graham St was evacuated.
A worker at the site told the New Zealand Herald the fire started in an elevator due to a spark from a welder.
The site was evacuated and the thick plume of smoke seen around the city was burning plastic, the worker said. A nearby crane was not affected by the fire.
Fire and Emergency New Zealand confirmed the fire was in an elevator shaft.
FENZ received the callout at 8.19am and no one was injured, a spokesman said.
The fire had now been extinguished.
A worker at the site said: "It was on level 6, flames everywhere, me and the other guys try to blitz it out with the fire extinguishers.
"There was too much oxygen in the air so we couldn't take it out."
The building under construction is the Safari Group's Ramada Hotel and Suites Victoria St, a $75m Auckland project with 66 private apartments and 48 hotel apartments.
The blaze was visible across the city, with thick plumes of black smoke drifting over the Auckland skyline.
Four fire engines attended and the fire was put out about 8.45am.
An ambulance was also in attendance.
