Home Postcodes by state WA 6161 Postcode 6161 6161 is the postcode for Rottnest Island, WA. Localities with postcode 6161Rottnest IslandWA Postcode 6161 State or territory Western Australia (WA) Localities 1 Council area Cockburn Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6160 · Postcode 6162