Fire Rescue Victoria (FRV) responded to several calls of a house in Lusher Road, Croydon with fire trucks arriving within 4 minutes.
By the time firefighters arrived the single-storey brick veneer home was well alight making entry difficult.
Fire-fighters from both FRV and CFA wearing breathing apparatus worked together to knock the fire down and enter the 20sq. m home.
The body of a man, still to be formally identified, was found in the house while a second man, also an occupant of the house, was not injured and taken to hospital for observation.
The fire was declared under control at 04:17am, 37 minutes after the first call was received.
Police and FRV Fire Investigators are treating the fire as suspicious with a crime scene established and arson chemist attending the site this morning to assist determining the cause of the fire.