Hydrodiplomacy is the emerged framework where legal acts, primarily based on technical data and information, aim at supporting commonly accepted solutions to water disagreements, tensions, disputes and conflicts among states with transboundary waters. Climate change and other socioeconomic pressures, e.g. human overpopulation, nevertheless, are bound to destabilize the core element of hydrodiplomacy, i.e. the water. In the research hydrodiplomacy components laid on a) policy aspects, such as cooperation agreements and common legal frameworks on water management, b) preventive aspects, such as socio-political tensions, mankind pressures on the hydrosystem and historical disputes among the riparians, c) cooperative aspects, such as joint development and research programmes and projects and d) technical aspects, such as quality and quantity status of the transboundary waters, are considered together with climate change features, expressed as e) climate change-related studies on the transboundary waters and as f) climate change-related ratified agreements and protocols, to assess the impact of climate change on the water-related transboundary cooperation. The case study area is composed of the five transboundary river basins of Greece shared with neighboring states. The coupling of all these different-nature elements is conducted with the use of the Analytical Hierarchical Process multicriteria method, and results on the development of a normalized index that quantifies transboundary cooperation on water management in the climate crisis era.