This building was the first purpose-built post office for Botany, and claimed as the first NSW post office built to Commonwealth architects' designs. Its external detail and finish was broadly Neo-Georgian and Colonial Revival in the manner suggested in William Hardy Wilson's well-known local designs of 1913 (Eryldene) or 1916 (Purulia), with a hipped terracotta roof in Marseilles-pattern tile (probably not original), boxed eaves, double-hung sash windows that have six-paned upper sashes, cement rendered external walls and Tuscan pillars framing the entries and four others flanking the windows of the retail space. The columnar motif in groupings or suggested groupings of four was an established signature in Murdoch and Mackennal's smaller Victorian post offices and was to some extent a carry-over from earlier Murdoch designs in Queensland such as Roma Courthouse. The public area was placed under a hipped breakfront and accessed from porch entries to either side, on the well-established Queensland and Victorian pattern. At some stage since its completion, the southwest porch's entrance has been boarded-in, and incorporated into the retail space. This porch's plaster ceiling finish is extant and visible within the retail space. The design is more like a residential-cottage in scale and demeanour than the monumentalised and usually elevated masonry post offices in Queensland and Victoria. The PO box area is located inside the remaining porch and also in an addition towards the rear of the building. A concrete driveway was added later to a car park area at the rear. This area was later fenced with galvanised chain link and steel tubing. A small front yard or garden area is in front of the entry side, and this may have been a lawn at some point. It is now brick paved in zigzag patterning, probably dating from the mid-1980s. A set of public phone booths was installed on the left front, along with a concrete framed park bench (later replaced with a lighter metal structure). Several additions have been made to the rear of the post office. A space now used as a lunchroom between the building's two toilets was probably the rear verandah of the original building, but has now been enclosed by an addition. A low ramp access has been fitted to the northeast porch and a metal frame glazed door has replaced the original doors. The windows have all been barred apart from those to the porch still in use at the northeast corner. The battened board ceiling remains in the retail space, but elsewhere ceilings are of more recent origin.