Mountains are of great significance for people and biodiversity. Although often considered to be at low risk from alien plants, recent studies suggest that mountain ecosystems are not inherently more resistant to invasion than other types of ecosystems. Future invasion risks are likely to increase greatly, in particular due to climate warming and increased human land use (e.g. intensification of human activities, human population growth, and expansion of tourism). However, these risks can be reduced by minimising anthropogenic disturbance in and around protected areas, and by preventing the introduction of potentially invasive alien plants into these areas, particularly at high elevations. Sharing information and experiences gained in different mountainous areas is important for devising effective management strategies. We review current knowledge about plant invasions into mountains, assembling evidence from all continents and across different climate zones, and describe experiences at local to global scales in preventing and managing plant invasions into mountain protected areas. Our findings and recommendations are also relevant for managing native species that expand to higher elevations.