The child fell off a walkway at Rob Roy Glacier, he said.
The helicopter has arrived at the scene and is taking the child to Dunedin Hospital.
The spokesman said earlier that the difficult terrain meant someone would need to be winched down to retrieve him.
The Department of Conservation website said the Rob Roy track was an easy route, achievable by older children.
It is a three-to-four-hour tramp, and it takes at least an hour to drive to the start of the track.
An alert on the website said there is an unstable slip on the lower section of the track that has a steep drop-off, and care is needed when crossing that section.