In recognition of the need to have effective procedures for notification and consultation in place, this article examines the current status of customary international law. This analysis largely focuses on the codification effort conducted by the International Law Commission (ILC), which in its contribution to the text of the Watercourses Convention, developed detailed rules on notification and consultation. However, the article identifies a number of areas where greater clarity is needed—that is, concerning the timing of notification, what data and information should be shared, and whether plans should be suspended for the duration of the notification and consultation period. The article then considers whether two recent cases, the 2010 Case Concerning Pulp Mills on the River Uruguay (Argentina v Uruguay) before the International Court of Justice (ICJ) and the 2013 Indus Waters Kishenganga Arbitration (Pakistan v India) in front of the Permanent Court of Arbitration (PCA), might offer interpretative guidance in addressing these unsettled areas. Additionally, the cases highlight some of the challenges in the implementation of procedures for notification and consultation and point to the need for further clarity.