Originally Posted by QF SYD Airport Guide

Transferring from T2 and T3 (Domestic Airports) to T1 (International Airport):

The Transfer Lounge is located airside (after passing through the security check point), at Gate 15 in T3. A shuttle bus service is available to passengers that are travelling or have travelled on a Qantas flight (including codeshare flights) or oneworld flight. The shuttle buses operate every 10-20 minutes from 6am to 9.40pm AEST. On arrival at T1 proceed up the escalator, through immigration and security to your departure gate.

Transferring from T1 (International Airport) to T2 and T3 (Domestic Airports):

The Transfer Lounge is located on the Arrivals level of Sydney International Airport. After you clear customs, follow the signs located outside the terminal, entry is external to the main terminal within a short walk via a weather protected walkway. Recheck your baggage at the Seamless Transfer Check-in counters and then board the shuttle bus for the Domestic terminal. It operates from 6am to 12noon every 10 minutes and from 12noon until 9.00pm AEST every 20 minutes. The bus arrives at T3 at Gate 15. Check the screens for departure gate information. Passengers connecting to a flight not operated by Qantas or QantasLink should refer to the Sydney Airport website for further information on transfer options.