Sergeant Steve Watt said the incident highlighted how the consequences of a single punch could be "extremely severe''.
"We're constantly saying to people that it only takes one punch to cause serious damage.
"It certainly has in this instance.''
Police were "continually monitoring'' the condition of the victim, who is Sri Lankan and had been working in Queenstown for "many years'' as a chef.
The assault occurred about 3.20am on Tuesday in Cow Lane, and was sparked by an altercation in a bar in Camp St between two pairs of men.
They were all kicked out of the bar.
About 20 minutes later, one of the alleged offenders came across one of the other men outside.
"He’s tried to confront him, and the victim’s just pushed him away," Sgt Watt said.
The offender then punched the victim in the head.
"He’s then hit the ground and hit his head on the ground."
The alleged offender then ran off.
The victim, who suffered a fractured skull, was taken by ambulance to Lakes District Hospital in a serious condition, and later flown to Dunedin.
The incident was captured on CCTV, and Sgt Watt said police were appealing for information.
