The post office portion of the building originally accommodated the postal, telegraphic and telephonic departments, as well as an upper floor residence for the postmaster.

In c. 1975, a single-storey addition was built to the east and rear of the original building, including a PO box lobby and room, new back offices and van bay.

[3][1] The original double-storey building was in two facets, expressing the shared usage, with the Institute adopting a projecting frontage with an astylar breakfront, and the Post Office, set back by about 600mm, a symmetrical elevation in its own right.

[1] Externally, North Adelaide Institute and Post Office's intactness is high with regard to the original form, material and detail, despite rear and side additions constructed in 1975.

The original rendered dressings have been overpainted and the usual component of signage, handrails and external services have been added, but the fabric is otherwise intact.

The post office has also played a prominent role in the affairs of North Adelaide and was one of a number of significant public buildings and structures erected in this period of prosperity and confidence in North Adelaide, the others being the Art Gallery, Mitchell Building, Jervois Wing of the Library, Public Baths, Rotunda and Torrens Weir.

Typologically, North Adelaide Post Office demonstrates all of the archetypal characteristics of a combined postal and telegraphic facility with telephonic and residential components.

The complex's substantial scale also assumes a major civic role in North Adelaide's high street and demonstrates the increased volume in communications of the period.

The broadly Italianate form, modulation and detail is also a harbinger of Federation architecture in Adelaide through introducing an exposed salmon-red brick facade and stilted windows with heavy architraves.

The building's composition, with its massing, symmetry and use of fine salmon red brickwork, stonework, rendered dressings and mouldings, all combine to give the structure outstanding aesthetic appeal.

[1] This Wikipedia article was originally based on North Adelaide Post Office, entry number 106136 in the Australian Heritage Database published by the Commonwealth of Australia 2019 under CC-BY 4.0 licence, accessed on 15 May 2019.