Mountains are hotspots for biodiversity and of great importance to human societies. The worldwide placement of mountain areas in conservation reserves is recognition of their value. Managers have to remain vigilant to protect mountain ecosystems from future threats. One such threat is invasive, non-native plants. Invasive plants alter plant communities, affect grazing lands and homogenise the world’s flora. Mountain areas have not been as intensely affected by plant invasions as low elevations because of harsh climatic conditions, isolation and limited human pressure. The relative resistance of mountain ecosystems to plant invasions may be transient, however, in light of ongoing global change (e.g. climate change, expansion of human pressures). Unique mountain flora, fauna and habitats may become increasingly susceptible to invasions.