This research aimed to provide a detailed review of selected transboundary basins to ascertain the application of ecosystem-based approaches and draw specific lessons for effective integrated water resources management in international contexts. Basins were selected to represent Africa, Asia and the Pacific, Europe, Latin America and the Caribbean, North America, and West Asia. The case studies represent regional variables while attempting to showcase a range of stresses and ecosystem service vulnerabilities. They focus on ecosystem services relevant to basin management, including climate regulation, water regulation, natural hazard regulation, energy, freshwater nutrient cycling, water purification and waste treatment, disease regulation, primary production, fisheries and recreation, and ecotourism. They include an analysis of whether ecosystem management principles are explicitly or implicitly applied in IWRM processes and whether the approaches recognize and are oriented towards managing bundles of ecosystem services, such as uplands watershed management through afforestation, which addresses the combined services of climate regulation, water regulation, and water quality. The case studies include The Congo River Basin, the Okavango River Basin, the Red River Basin, the La Plata River Basin, the Danube River Basin, the Mekong River Basin, and the Jordan River Basin.