In the existing 276 international river basins, the increase in water variability projected by most climate change scenarios may present serious challenges to riparian states. This research maps the institutional resilience to water variability in transboundary basins and combines it with both historic and projected variability regimes, with the objective of identifying areas at potential risk of future hydropolitical tension. To do so, it combs existing international treaties for sources of institutional resilience and considers the coefficient of variation of runoff as a measure of past and future water variability. The study finds significant gaps in both the number of people and area covered by institutional stipulations to deal with variability in South America and Asia. At present, high potential risk for hydropolitical tensions associated with water variability is identified in 24 transboundary basins and seems to be concentrated mainly in northern and sub-Saharan Africa. By 2050, areas at greatest potential risk are more spatially dispersed and can be found in 61 international basins, and some of the potentially large impacts of climate change are projected to occur away from those areas currently under scrutiny. Understanding when and where to target capacity-building in transboundary river basins for greater resilience to change is critical. This study represents a step toward facilitating these efforts and informing further qualitative and quantitative research into the relationship between climate change, hydrological variability regimes, and institutional capacity for accommodating variability.