Home Postcode finder SA Nepean Bay Nepean Bay postcode SA Nepean Bay 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 Nepean Bay business listing Be the first listing in Nepean Bay Common questionsWhat is the postcode for Nepean Bay?Nepean Bay, SA has the postcode 5223.What state is Nepean Bay in?Nepean Bay 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 Nepean Bay. Browse other postcodes in South Australia, or widen the search to every Australian postcode.