Home Postcode finder SA Arno Bay Arno Bay postcode SA Arno Bay is a locality in South Australia covered by postcode 5603. Postcode 5603 State or territory South Australia (SA) Region SA Outer Suburbs Add a free Arno Bay business listing Be the first listing in Arno Bay Common questionsWhat is the postcode for Arno Bay?Arno Bay, SA has the postcode 5603.What state is Arno Bay in?Arno Bay is in South Australia (SA).Does postcode 5603 cover more than one suburb?Yes. Postcode 5603 covers 4 localities, so the postcode alone does not identify Arno Bay. Browse other postcodes in South Australia, or widen the search to every Australian postcode.