Home Postcode finder QLD Johnstown Johnstown postcode QLD Johnstown is a locality in Queensland covered by postcode 4615. Postcode 4615 State or territory Queensland (QLD) Region Toowoomba Region Add a free Johnstown business listing Be the first listing in Johnstown Common questionsWhat is the postcode for Johnstown?Johnstown, QLD has the postcode 4615.What state is Johnstown in?Johnstown is in Queensland (QLD).Does postcode 4615 cover more than one suburb?Yes. Postcode 4615 covers 19 localities, so the postcode alone does not identify Johnstown. Browse other postcodes in Queensland, or widen the search to every Australian postcode.