Eureka man Kenny Watson ran to his neighbour's house after hearing an explosion, then broke down the back door and letting the cat out.
He then when back to the front of the house where the fire had started and put much of it out with the garden hose.
There was still significant damage to the sharehouse, but the CFA said army veteran Mr Watson's actions saved the unoccupied house from burning down.
The fire destroyed the front left corner of the house and the rest was smoke-damaged.
"I heard an explosion, and looked over and then front of the house was engulfed. I ran across the creek and knocked on the windows to wake anyone up if they were sleeping, then kicked in the back door, and the cat came out. I had a look around but it was pretty smoky," said Mr Watson.
"(Then) I pulled out the garden hose and put the fire out."
Three CFA units attended the scene to finish putting the fire out.
Incident commander Peter Higgins said he was impressed with Mr Watson's actions.
"He's done a bloody good job," he said, but also made clear not everyone should try and put out a fire alone.
"I wouldn't recommend everyone do that, be aware of the your own capabilities."
A cigarette butt is suspected to have caused the fire, which then blew up an aerosol can, alerting Mr Watson, who was in the army for four years.
He said he was happy he let the cat out, because he also had animals and would be "devastated" to lose any of them.
The CFA also rescued a rabbit from the blaze.