Fire and Emergency New Zealand acting shift manager Jon Ditmer said an automatic alarm alerted firefighters to the incident at the George St facility at 1.22pm, which was followed shortly after by a 111 call.
Units were sent from Willowbank, Dunedin and St Kilda stations, backed up by Roslyn and Ravensbourne.
The fire was contained, and units had left the scene by mid-afternoon.
Woodhaugh Station Officer Mark Townsend said the cause of the fire was undetermined, and the fire investigation team had been notified.
The rest-home staff had done an efficient job of evacuating the residents, and nobody had been injured.
There was smoke damage to the room involved and some to the room next door, and water damage because sprinklers activated.
"It was early detection and a good evacuation process."
