On 21 May 1997, at the UN General Assembly, an overwhelming majority of States voted for the adoption of the United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses – a global overarching framework governing the rights and duties of States sharing freshwater systems. To date, the Convention counts 17 Contracting States – 18 short of the number required for entry into force. This article examines whether and why States should support the Convention towards ensuring its entry into force. We first look at the governance of international watercourses in order to illustrate the relevance of the Convention. The article also examines the Convention's drafting and negotiation process, the subsequent practice of States, some possible reasons slowing down ratifications and the likelihood of entry into force in the foreseeable future. Noting the widespread State support for the Convention in 1997, we conclude that, while various reasons have possibly prevented that support from translating into entry into force, the need for an effective UN Watercourses Convention has not diminished. In view of current human and environmental threats to the world's water resources, coupled with the poor governance of transboundary watersheds, the potential role that the Convention could play, once in force and widely ratified, as discussed, may in fact be more critical than ever.