williamstown postcode sa Home ›› Postcode Finder ›› SA ›› Williamstown Williamstown local listingsThe suburb of Williamstown is located in SA and has a postcode of 5351. Free williamstown business listing! 1Williamstown Primary School5 Margaret St 08 85246289 View more business listings in williamstown Search and find other Postcodes in South Australia or widen the search to Postcodes in Australia.