Most government offices in the Hambantota district are currently located in private houses after tidal waves in December 2004 destroyed large numbers of state buildings.
The four story office block will house Central, provincial and local government institutions that are now scattered in separate buildings around the area.
The government will put in five million dollars towards the 25 million dollar project cost to build the complex, the Finance Ministry said in a statement on Monday.
The Korean government is also considering eight million dollars in grant aid to build an International Convention Centre at the proposed complex.