In the mid-1870’s, German companies established the first trading ties within the area that would become German New Guinea.  In 1884, the German flag was raised over several coastal towns, and the Neu Guinea Kompagnie was chartered to administer the area in 1885.  This included the ability to administer postal services.

On 1 April 1899, the German government assumed responsibility for administering the colony, citing the inability of private sources to finance the necessary development within the colony.

On 4 February 1906, a post office was opened at Simpsonhafen, which was also made the capital of the colony.  On 1 April 1910, the town was renamed to its native name, Rabaul. 

The Rabaul post office would close on 12 September 1914, when the town was occupied by Australian forces.