The fire, which began in the front office of Vision Antenna Systems on Portsmouth Dr shortly before 1am, was noticed by a passing police officer while attending to a routine traffic stop.
Fire appliances from Lookout Point, Roslyn and St Kilda were called to the scene.
Meanwhile, company co-owner Glen Stapley was heading to the premises after being notified by his monitored alarm system about a possible burglar in the building.
"I was expecting to find a burglar, but instead there was a cop and all these flashing lights there," Mr Stapley said.
He said he credited the quick actions of the police officer with preventing the fire from being much worse.
The business, which specialises in antenna and audio visual equipment, was insured and the damage was estimated at $100,000, he said.
Southern Region fire safety officer Stuart Ide said it appeared the fire was caused by an electrical multibox.
The fire served as a reminder to businesses to have their alarms connected directly to the Fire Service, he said.
"In situations like this, the faster the Fire Service can get there with an early response, the better."
