Although the eastern Himalayas have high plant biodiversity, we know very little about plant invasions in the region. This study is the first to examine non-native plant distribution in a popular eastern Himalayan national park. A total of 61 non-native plant species were found in roadside plant communities, which are frequently disturbed by hikers, pack animals, and recreational vehicles. These species were annual or biennial herbs, most of which originated in America or Europe. Non-native plant richness varied with the degree of anthropogenic disturbance. Specifically, greater numbers of non-native species were found at road heads and ends, which are generally subject to intense human activity. The average number of non-native species also varied according to the type of road and road use, with more present along motor roads and horse-riding trails than along hiking trails. These results highlight the role of vehicles and pack animals as dispersal vectors and provide a foundation for future invasion management decisions. To prevent the spread of non-native plants from park roads to the adjacent landscape, we also recommend the development of educational and monitoring programs that encourage tourist participation in conservation efforts.