The Former Customs House is a stuccoed structure erected from 1873, to designs presumably by the Public Works Department of Victoria, to serve as a Custome House, offices and residence. The double storey, symmetrical main facade has single storey porches at each end, repeating the arched window motif. The upper floor has window hoods and balconettes on brackets, with elaborate eaves brackets and hipped slate roof above.
The Customs House is a unique illustration of the thriving port town that was Williamstown in the nineteenth century. It has considerable landmark and streetscape importance in the historic city and is architecturally important for its design and detailing and as an example of the rare Customs House building type. The Conservative Classical design is a notable example of the work of the Public Works Department and is largely intact and in good condition, complete with iron palisade fence.