The incident, on Sunday evening, is the airline's fifth turnback in the past week.
Pilots on the Boeing 737 aircraft flight QF102 from Nadi, in Fiji, to Sydney requested a priority - not emergency - landing on Sunday and the aircraft landed normally.
Early indications were the fumes related to the oven in the aircraft galley.
They dissipated quickly and no one was impacted.
Engineers will assess the aircraft.
Qantas was working to accommodate customers as quickly as possible and thanked them for their patience.
The incident follows a similar event last week.
On Thursday, Qantas said QF101, a Boeing 737 bound for Nadi, returned to Sydney after an onboard "fault indicator" about a possible mechanical issue.
A Qantas representative told AAP the pilots followed standard procedures and the aircraft landed normally in Sydney.Â
The plane returned without emergency or priority landing and the fault indicator did not relate to an engine issue, Qantas said.
Three Qantas flights were also diverted on Friday - a QantasLink service from Melbourne to Canberra; a Boeing 737-800 from Melbourne to Sydney; and a flight from Adelaide to Melbourne.
On Wednesday, the pilot of QF144 - a Boeing 737 - from Auckland to Sydney shut down an engine and made a mayday call over the Pacific Ocean before landing safely at Sydney's Kingsford Smith Airport about 3.30pm.
Transport safety investigators confirmed they would analyse QF144's cockpit voice recorder and flight data after the engine failure.
Qantas said all 145 passengers disembarked normally and shutdowns were rare, with pilots trained to manage them safely.
The Qantas Group averages about 60 air turnbacks per year from more than 10,000 across the total industry.
The Civil Aviation Safety Authority said on Friday it was confident Qantas was operating safely and has confidence in its safety management systems.
