Home Postcode finder WA Holt Rock Holt Rock postcode WA Holt Rock is a locality in Western Australia covered by postcode 6355. Postcode 6355 State or territory Western Australia (WA) Region Wa Subs 2 Gsr Add a free Holt Rock business listing Be the first listing in Holt Rock Common questionsWhat is the postcode for Holt Rock?Holt Rock, WA has the postcode 6355.What state is Holt Rock in?Holt Rock is in Western Australia (WA).Does postcode 6355 cover more than one suburb?Yes. Postcode 6355 covers 11 localities, so the postcode alone does not identify Holt Rock. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.