In this chapter we discuss the vulnerability of mountain forest ecosystems to climate change, considering that vulnerability is determined by the combined effects of exposure, sensitivity, and the adaptive capacity of forest ecosystems in a socio-ecological context. Drawing on a 10-year monitoring program along an altitudinal transect in the mountain forests of the Panguipulli District in southern Chile, we demonstrate the differentiated sensitivity of forest types to climate change in terms of tree growth, regeneration, and associated understorey plant species. Lenga (Nothofagus pumilio) and Araucaria (Araucaria araucana) forests, located near the upper treeline, show the highest vulnerability due to their restricted range, slow growth, and limited adaptive capacity, while mid-altitude forests such as Coihue–Raulí–Tepa and Roble–Raulí–Coihue exhibit comparatively greater resilience but still face growth reductions and compositional shifts after the 2016–2017 and 2022–2023 extreme heatwaves associated with the prolonged Chilean megadrought (2011–2020). These impacts directly affect key ecosystem services, including water provision, sediments and nutrients retention, scenic beauty, timber production, and non-timber products. We conclude that effective adaptation to climate change in these landscapes will require a dual approach that combines the strict conservation role of parks and reserves with targeted adaptive management practices in actively managed forests, thereby sustaining both ecosystem resilience and the well-being of the local communities who depend on them.