This study aimed to determine the effect of diplomacy in the manufacture of Chinese hydropower dams on the downstream states of the Mekong River. This article mobilises the political economy literature to see how China influenced countries in the Mekong River to agree with the Chinese hydropower dam projects. The article shows that hydropower dams are not only part of China's soft power but are instruments to support China's economic and political ambitions. Therefore, the success or failure of dam construction depends on the agreement and the level of bilateral political relations and the countries that establish cooperative relations for hydropower dams. Despite the benefit it can give, this development also negatively impacts countries like Laos and Cambodia. The impact can be seen in erosion, flooding, destruction of breeding fish habitats and population movements.