Transboundary watercourses constitute an important reservoir providing perhaps the most critical natural resource essential to support life all over the world. Many governments depend on rivers straddling two or more countries to provide not only freshwater for their populations, but also hydro-electric power sources, recreation and other forms of socio-economic sustenance. The article is focused on the international legal regulation of the Zambezi River as one of the most significant international watercourse. Being the forth longest river in Africa, the Zambezi is shared by eight Southern African States and evaluates a quarter of a century of close cooperation in order to realize the Southern African Development Community (SADC) founding principles.