This study was undertaken to document alien and invasive flowering plant species in the Western Ghats (Hassan district, Karnataka, India), with background information on family, habit, habitat, longevity, nativity, and uses. A total of 312 alien species belonging to 236 genera in 79 families are listed. The majority belong to family Asteraceae (36 species), followed by Fabaceae (21 species), and Amaranthaceae (17 species). Herbs constitute the majority (59%) of alien species followed by shrubs (17 %). Around 36% the alien taxa are native to tropical America. Of 314 alien species, 122 were intentional introductions, with a majority (39%) introduced for ornamental purposes; 24% of species have naturalized, while 33% display as invasive. There is an urgent need to gather regional data on the diversity of invasive alien plant species in order to study the impact on native vegetation and biodiversity.