Home Postcode finder SA Seaton North Seaton North postcode SA Seaton North is a locality in South Australia covered by postcode 5023. Postcode 5023 State or territory South Australia (SA) Region Adelaide Add a free Seaton North business listing Be the first listing in Seaton North Common questionsWhat is the postcode for Seaton North?Seaton North, SA has the postcode 5023.What state is Seaton North in?Seaton North is in South Australia (SA).Does postcode 5023 cover more than one suburb?Yes. Postcode 5023 covers 3 localities, so the postcode alone does not identify Seaton North. Browse other postcodes in South Australia, or widen the search to every Australian postcode.