The present study aimed to observe the floristic diversity and phytosociological analysis of alien weeds of Coconut Plantations in Kanyakumari District. One sixty one species belonging to 125 genera and 46 families were identified. Of these 31 families were dicot, 14 families were monocot and 3 families were Pteridophyte. Vegetation data were collected by quadrate method and analysed for density, frequency, important value index (IVI), shannon-weiner diversity index, simpson index, wittaker index and whitford index for each crop ecosystems. The three dominant weed families in the study area were Asteraceae, Poaceae, Cyperaceae. Chromolaena odorata was found as dominant in site 1,2,4,5 and Cyanodon dactylon, Ipomea –pes-caprae was found as dominant in site 3 with Important Value Index (IVI) of (Site 1) 5.3,(Site 2) 7, (Site 3) 9.41, (Site 4, 5)7.8.