Home Postcode finder WA Monjingup Monjingup postcode WA Monjingup is a locality in Western Australia covered by postcode 6450. Postcode 6450 State or territory Western Australia (WA) Region Wa Subs 1 G Flds Add a free Monjingup business listing Be the first listing in Monjingup Common questionsWhat is the postcode for Monjingup?Monjingup, WA has the postcode 6450.What state is Monjingup in?Monjingup is in Western Australia (WA).Does postcode 6450 cover more than one suburb?Yes. Postcode 6450 covers 23 localities, so the postcode alone does not identify Monjingup. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.