Home Postcode finder SA Middle River Middle River postcode SA Middle River is a locality in South Australia covered by postcode 5223. Postcode 5223 State or territory South Australia (SA) Region Sa Subs Near 2 Add a free Middle River business listing Be the first listing in Middle River Common questionsWhat is the postcode for Middle River?Middle River, SA has the postcode 5223.What state is Middle River in?Middle River is in South Australia (SA).Does postcode 5223 cover more than one suburb?Yes. Postcode 5223 covers 30 localities, so the postcode alone does not identify Middle River. Browse other postcodes in South Australia, or widen the search to every Australian postcode.