The flight carrying over 470 passengers and 27 crew members returned to Sydney International Airport about an hour after take-off, The Straits Times reported.
The airline did not specify what the technical issue was.
It was scheduled to leave Sydney at 11 a.m. local time and land in Singapore at 5:30 p.m., but landed at 10.24 p.m. instead, Channel News Asia reported.
"Singapore Airlines sincerely apologizes to all affected customers for any inconvenience caused," the airline said in a statement, adding that passengers were provided with refreshments and all necessary assistance.