Further details are being sought from Air New Zealand.
A Fire Service communications spokesman said it was not clear exactly what the issue was yet and they would know more after the plane had landed.
Air New Zealand spokeswoman Emma Field said the plane was being inspected by engineers after landing "without incident" shortly before 10am.
"Flight NZ103 from Auckland to Sydney returned shortly after take-off this morning as a precaution after an unusual smell was detected in the cockpit."
The Dreamliner had been taken out of service for the time being.
Customers booked to travel on this service were being re-accommodated on an alternative service, Field said.