This article investigates the motives and incentives that drive countries' diplomatic efforts in water disputes. It aims to identify links between the formation of water management institutions (WMIs) and the outcomes of such institutional cooperation. Three features have been identified as key to the effectiveness of WMIs: (1) the development of trust; (2) sanctions aimed at curbing cheating; and (3) the balancing of different countries’ interests over shared waters. This article conducts a comparative analysis of the formation of institutional arrangements among three riparian states by focusing on two cases: water interactions between China and India, and between India and Bangladesh. It argues that India, China and Bangladesh have exhibited different preferences in regard to their participation in WMIs. The two cases illustrate how different WMIs are formed and also how, in proportion to variations in the level of competition over water quantity, diplomatic cooperation through environmental agreements can lead to different outcomes with varying degrees of success. This article concludes that in the context of the global South, where foreign relations are unstable and countries’ reliance on river basins varied, building trust and balancing interests over water management are especially important to the formation of effective institutional arrangements.