Sister City/Sister Province Cooperation Agreement is a regional cooperation that is capable for opening a good investment space for the country’s revenue. These days, Sister City/Sister Province Cooperation Agreement is no longer limited to cooperation in strengthening the diplomatic relations but also has its economic benefits. Sister City/Sister Province Cooperation Agreement is one of the treaties that concluded by the Local Government. The Local Government has a major role with the regional autonomy. In order to conclude a Sister City/Sister Province Cooperation Agreement the Local Government must follow series of mechanisms. The authority to conclude a Sister City/Sister Province Cooperation Agreement is based on Act on Local Government. This research has the purpose to find any similarities or differences of the Act on Local Government from 1999 to 2014. This research uses a normative juridical approach, where data sources obtained from the primary legal materials, secondary, and tertiary. The results showed that the Act on Local Government does not give a detailed explanation on the conduct of Sister City/Sister Province Cooperation Agreement. More detailed rules actually contained in the implementing regulations such as the Regulation No. 3 of 2008 on Guidelines for Local Government Cooperation with Foreign Parties and General Guide Procedures for Foreign Relations and Regulation No. 09/A/KP/XII/2006/01 on Cooperation by Local Governments published in 2012. But, the implementing regulations mentioned are still not accordance to the prevailing law.