Crews from the CFA responded to reports of a house fire on Duncan Street in Fyansford at around 3:23 pm.
Five CFA units from Geelong and Geelong West attended, along with FRV, Victoria Police, and a representative from Geelong City Council.
Upon arrival, crews found a 15m x 20m abandoned building fully engulfed in flames and immediately began containment efforts.
The incident was declared under control by 4:20 pm, though crews continue to monitor the scene.