He told the GNA that the Western Regional Coordinating Council provided offices for the unit while the United States Agency for International Development (USAID) provided funding for their refurbishment.
Mr Mahama said the unit is the first of its kind in the country and similar units are to be established in the Ashanti, Brong-Ahafo and the Eastern Regions under a pilot project.
He said technical supports units would be set up in all regions if the pilot project is successfully implemented.
Mr Mahama said the unit would provide technical support and direction for HIV activities implemented in the region.
He said in view of the influx of all manner of people into the region due to the discovery of oil in commercial quantities, there is the need for financial support and a vigorous pursuance and implementation of key and result oriented interventions that could facilitate a further reduction of HIV prevalence in the region.
Mr Mahama said "the establishment of the TSU in the Western Region as a way of ensuring decentralization of the wings of the Ghana AIDS Commission is the most important step towards enhanced coordination, monitoring and evaluation"