Home Postcode finder WA Millstream Millstream postcode WA Millstream is a locality in Western Australia covered by postcode 6716. Postcode 6716 State or territory Western Australia (WA) Region North West Suburbs Add a free Millstream business listing Be the first listing in Millstream Common questionsWhat is the postcode for Millstream?Millstream, WA has the postcode 6716.What state is Millstream in?Millstream is in Western Australia (WA).Does postcode 6716 cover more than one suburb?Yes. Postcode 6716 covers 4 localities, so the postcode alone does not identify Millstream. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.