A Qantas spokesperson says the captain of flight QF17, which was carrying 199 passengers and 21 crew, decided to return to Sydney an hour into the flight to Buenos Aires.
Qantas engineers are investigating a panel in the cockpit, which began emitting smoke.
Earlier this month the engine of a Qantas Airbus A380 exploded over Indonesia. Qantas and Singapore Airlines grounded their A380s while the explosion was investigated.
A day later, a Qantas Boeing 747 was forced to turn back from Singapore en route to Sydney when an engine failed.
On Friday, a Qantas 767 turned back to Perth after vibrations were detected in one of its engines.