In 1946 District Office of Tambunan is headed by a Chief Clerk, under the jurisdiction of District Office Keningau. The District Officer of Keningau makes a visit to Tambunan once in a month. The District Office of Tambunan was upgraded to a District administration in 1948 that was three (3) years after the second World War. The first District Officer was OKK Tambakau.

In 1948 the District office was housed in a temporary building made from bamboo. In 1949 the District administration moved to a new building( Presently occupied by Land and Survey Department).

Due to the rapid development the District Administration moved to a bigger and more modern office that is still being occupied presently, in 1979.

The District is administered based on the basic function implemented by the British, but somehow changes has occurred in terms of emphasis, objective and coverage. More emphasis was given for the development, while the main objective is to upgrade the living standard of the people , eradication of poverty and restructuring of the community, to ensure that the state's wealth and natural resources are being equally distributed.