Auckland Hospital spokeswoman Jennifer Dann said the man's condition was serious but stable at about 12pm.
Police have launched an investigation into the attack and the offenders have not been identified.
Businesses at the central city intersection said they did not see or hear the incident.
Shakespeare Hotel and Brewery's David Holdstock said the employee who was working the nightshift had not handed any details over.
A Barclay Suites employee also said there had been no reports of the incident and the hotel's CCTV footage did not show anything.
She said security on the night shift would report any incident they were aware of.
Police want to speak to anyone who witnessed the assault or has any information.
Call the Auckland City Crime Squad on (09) 302 6557.