The Alps and the Andes are both considered water towers in their respective continents and are thus significant not only for their own water needs but also for those of lowland regions farther downstream. As climate change impacts on the hydrology of mountain regions are increasingly observed, attention is turning to the adaptive capacity of the water governance regimes in mountain communities. This paper explores the adaptive capacity of two contrasting water governance regimes in the Swiss Alps and the Chilean Andes. It assesses adaptive capacity by analyzing a set of governance-related adaptive capacity indicators in the context of recent extreme events, which serve as proxies for future climate change. Across these highly contrasted governance contexts, analysis reveals both similar and distinct institutional challenges for developing and mobilizing adaptive capacity in relation to climatic uncertainty and change. It also identifies emergent tensions related to temporal and spatial scales. Conclusions point to the need to focus on challenges relating to trust, integration of hydroclimatic information, and flexibility and iterativity of rules and plans across governance scales to better manage the exacerbating impacts of both climate variability and climate change.