Home Postcode finder WA Castletown Castletown postcode WA Castletown is a locality in Western Australia covered by postcode 6450. Postcode 6450 State or territory Western Australia (WA) Region Wa Subs 1 G Flds Add a free Castletown business listing More business listings in Castletown Businesses in CastletownCastletown Primary School43 Easton Rd · 08 90715599 Common questionsWhat is the postcode for Castletown?Castletown, WA has the postcode 6450.What state is Castletown in?Castletown is in Western Australia (WA).Does postcode 6450 cover more than one suburb?Yes. Postcode 6450 covers 23 localities, so the postcode alone does not identify Castletown. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.