Fenz said they received a call to the fire about 10:20pm. One appliance each from the Willowbank and Dunedin stations initially attended; when it became apparent the fire was "well involved", additional engines were dispatched from the St Kilda and Roslyn stations.
The fire had spread to multiple storeys of the house, Fenz said.
The fire had drawn a crowd of onlookers, and Fenz urged people to remain indoors as they worked to control the fire, which they described as "mostly extinguished". Part of Forth St had been closed.
Fenz said to their knowledge no-one had been hurt in the blaze.