Flight QF1608 made it about 100km, as far as Northam, according to flight tracking website Flightradar24, before landing safely back in Perth just after 5pm.
Perth airport said there were no reports of any injuries or major issues on board.
Qantas are investigating.
It marks the second Qantas flight in as many days that’s been forced to turn back.
This week’s hiccups mark the latest in a line of issues for the embattled Australian airline, with several incidents in the few weeks and months.
Despite five flights being turned around mid-air in the past week, the International and Domestic CEO claims there are “absolutely no issues” with the airline.