The oldest Post Office building in Victoria and was, at the time of its erection, one of the largest and most important, as it was the centre of the Maritime mail.
Built in 1859 to a Public Works Department design, it was a simple, slate-roofed, two-storey stone structure with stucco facades and with a single-storey verandah facing Hobsons Bay.
The first floor provided living quarters for the Postmaster; the ground floor contained kitchen and mail room. Extensions in 1895 made major changes to the street elevations, converting the colonial style of the building to Tudor, with added half-timbered gables, flat arch windows and polygonal chimneys.
Although internally much altered, the overall form of the building is intact from the 1895 additions. The kitchen, stair hall and staircase survive intact from 1859.