Six fire crews were called to Magnetic St at 4.40pm after fire engulfed the single-storey house.
Dozens of neighbours watched from the footpath as thick black smoke poured from the roof of the house.
A Fire and Emergency NZ spokesman said firefighters were informed someone was still in the house when they arrived.
They were able to extricate the person, whom a St John spokeswoman said was taken to Dunedin Hospital in a serious condition.
A neighbour said they believed only one person lived at the house.
Watching firefighters trying to bring the fire under control, neighbour Donna French said the damage to the house was also a personal loss.
Her grandparents used to live in the house, and she remembered running there to visit as a child.
"A lot of work went into that house. It is very sad."
Another neighbour believed the house’s current owner had recently finished renovating and installing solar panels.
The FENZ spokesman said three crews remained at the scene, dampening down the property, at 7pm.
A police scene guard would remain in place overnight, and a fire investigator was expected at the scene this morning.
It was the second serious house fire in the South yesterday.
A house in Bluff also suffered damage after a fire broke out yesterday morning.
Nobody was home there at the time.
