The former passenger jet was deployed as a water-bombing aircraft in New South Wales on Thursday and Friday.
It can carry more than 15,000 litres (4,000 gallons) of water and fire retardant - a large amount, though less than some other water-bombing planes.
However, officials say it offers greater flexibility because it can hold up to 63 firefighters in addition.
The plane dropped several loads of retardant on a fire that has threatened houses at Port Stephens, 150km (90 miles) north of Sydney.
Late on Friday local time, the blaze was not considered an immediate threat to lives. It had burnt through about 1,500 hectares.
The 737 was converted into an air tanker by Canadian company Coulson Aviation, and is on contract to the NSW Rural Fire Service.
The fire-fighting agency has nine other water-bombing aircraft, including one with a 45,000-litre capacity.
However, spokesman Chris Garlick said the modified 737 was a "more versatile" option.
"It's got all the capacity to drop big loads of water and retardant, but because it was a former passenger plane, we can also carry people in it and across interstate lines," he told the BBC.
Mr Garlick said they were "stoked" with how it had performed.
The fire has damaged some minor structures, such as sheds, amid strong winds.
Earlier this week a giant dust storm moved across the state, which has endured months of drought.
The state's bushfire season runs from October until April.