Home Postcode finder WA Southern Brook Southern Brook postcode WA Southern Brook is a locality in Western Australia covered by postcode 6401. Postcode 6401 State or territory Western Australia (WA) Region Wa Subs 1 G Flds Add a free Southern Brook business listing Be the first listing in Southern Brook Common questionsWhat is the postcode for Southern Brook?Southern Brook, WA has the postcode 6401.What state is Southern Brook in?Southern Brook is in Western Australia (WA).Does postcode 6401 cover more than one suburb?Yes. Postcode 6401 covers 18 localities, so the postcode alone does not identify Southern Brook. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.