We present results of the first major attempt to record the distribution of aquatic alien species in the Western Ghats Biodiversity Hotspot using Geographical Information System. A total of 32 alien species, including four macrophytes (Salvinia molesta, Pistia stratiotes, Eichhornia crassipes and Cabomba furcata) and 28 fish were recorded from the southern part of the Western Ghats. Seven of these have established natural populations and are invasive, which includes Oreochromis mossambicus, O. niloticus (Cichlidae), Poecilia reticulata, Gambusia affinis (Poeciliidae), Pterygoplichthys pardalis (Loricariidae), Cyprinus carpio (Cyprinidae) and Clarias gariepinus (Clariidae). Oreochromis mossambicus is the most extensively distributed invasive fish in the region. Major reservoirs serve as a spawning hub for species such as C. gariepinus and C. carpio. Significant pathways for the establishment of most alien species in Western Ghats were aquarium trade and aquaculture. Given the increasing records of alien species and proliferation of invasive species in the southern region of the Western Ghats, urgent research and policy interventions are suggested, including the development of a comprehensive database on distribution, trade, invasion biology, as well as determining both short-term and longterm impacts on endemic fauna.