The First Post Office is the first purpose-built building constructed for postal services in Brčko. It is located in the Kolobara residential area, near Islahijet and the Kočić House.
The Brčko Post Office first opened its doors in 1864.. At the time, only one clerk worked at the post office, and all postal traffic was carried out with Bosanski Šamac, Zvornik, Tuzla and Sarajevo. The post office used a stamp that was in use from 1865 to 1878. The stamp bore the inscription in Turkish: POSTEHANA BRČKI, meaning Post Office Brčko.

The building is single-storey and has an L-shaped layout with two asymmetrical wings, covering a total area of 511 square metres. The total height of the building is approximately 8.4 metres. The façade features 14 openings, of which 13 are windows.
The street façades are designed in the Neo-Renaissance style, reflected in the regular rhythm of window openings emphasised by a cornice and the horizontal division into shallow bands. Along the entire length of the building, The roof cornice is slightly projecting and profiled, with a characteristic horizontal gutter. Below it runs a shallow frieze, ending in a horizontal moulding that extends along both main façades. The cornice, frieze and horizontal moulding, together with the rows of windows, give the building its distinctive appearance.
The First Post Office has been designated a National Monument of Bosnia and Herzegovina.