Home Postcodes by state WA 6321 Postcode 6321 6321 is the postcode for Cranbrook, WA. Localities with postcode 6321CranbrookWA Postcode 6321 State or territory Western Australia (WA) Localities 1 Council area Cranbrook Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6320 · Postcode 6322