castletown postcode wa Home ›› Postcode Finder ›› WA ›› Castletown Castletown local listingsThe suburb of Castletown is located in WA and has a postcode of 6450. Free castletown business listing! 1Castletown Primary School43 Easton Rd 08 90715599 View more business listings in castletown Search and find other Postcodes in Western Australia or widen the search to Postcodes in Australia.