Tropical rainforests are distinguished from all other terrestrial ecosystem with high diversity of species and life-forms and are the most heterogeneous of the world ecosystems. Andaman Islands are a treasure of plant and animal diversity and home to four aboriginal tribes. namely the Andamanese, Onges, Jarawas and Sentenelese. A century-old cultural history of human occupation in these islands and indiscriminate utilization of plant resources by humans in the recent past, have posed serious threat to biodiversity. The study island Little Andaman although disturbed due to plantation of oil palm, tourism and related activities, harbours rich flora including endemics, and constitutes one of the important forests in the Indo-Burma biodiversity hotspot. In the study, the tree species richness, density and basal area were greater in all the undisturbed forests as compared to the disturbed forests. In understory plants, weeds formed about 1/4 of the species richness and density and the maximum diversity of weeds were recorded from the disturbed sites. The disturbed sites harboured lowest tree species richness and the highest understory plant species richness due to bioinvasion of weeds.