Multilateral agreements are in vogue in the world of international organizations and reflect a growing desire to strengthen hydro-diplomacy to prevent conflicts over the sharing of transboundary waters. However, such sharing is historically pre-empted by bilateral agreements between states. In this context, we question the capacity of multilateral agreements for the management of transboundary waters to be drivers of environmental hydro-diplomacy. We show that while these agreements do not directly resolve the obstacle of the territorial sovereignty of States and political issues as in the case of the Jordan River basin, nor that of the quantitative sharing of transboundary waters, they do create spaces for dialogue federated by environmental issues as shown in the case of the Danube River basin, tempering unilateral actions and contributing smoothly to a redistribution of roles towards non-state actors.