Mountain biodiversity and ecosystems have not yet been heavily affected by biological invasions. However, recent studies indicate that there are already at least some 1,500 non-native plant species present in mountain regions worldwide. Most of these non-native species were recorded only in one or a few mountain regions, and it can be assumed that many more non-native plant species are present in mountain regions not yet studied. Conservation managers consider at least 100 of these species as problematic. Climate change, increased land use intensity and increased transportation, will most probably significantly increase the risk of plant invasions into mountains in the near future. Due to warmer temperatures lowland invasive plants will spread into mountain ecosystems. An intensification of land use at high elevations may lead to increased introduction rates of non-native plants (propagule pressure) and anthropogenic habitat disturbances, and thereby further enhance future invasion risks. Mountains contain some of the very few ecosystems not yet severely affected by plant invasions. This gives researchers and managers the unique opportunity to respond in time to this emerging threat. Preventive measures may include the regulation of new plant introductions, especially of mountain specialist plants, the establishment and maintenance of a comprehensive monitoring system, and awareness building and networking with stakeholders (e.g. the horticultural and tourism industries and the general public).