A study was conducted to investigate the biodiversity and ecological roles of angiosperm plant parasites and weeds, focusing on parasitic and non-parasitic species in selected regions of the Indian Sundarbans. A total of four angiosperm parasites and eight weed species belonging to eight taxonomic families (Loranthaceae, Asclepiadaceae, Poaceae, Cyperaceae, Aizoaceae, Chenopodiaceae, Convolvulaceae and Amaranthaceae) were recorded from the study area. Plants of Loranthaceae and Asclepiadaceae have diverse host preferences. The infestation of parasitic angiosperms, viz. Hoya parasitica, Viscum orientale, Viscum monoicum and Dendrophthoe falcata, were primarily recorded in the canopies of specific host plants with a preference for Xylocarpus granatum, Xylocarpus mekongensis, Heritiera fomes and Bruguiera spp. in the intermediate and upper canopy zones; whereas, Sonneratia apetala, Excoecaria agallocha, and Avicennia officinalis were recorded as rarely infested mangrove species. Porteresia coarctata and Cyperus malaccensis were two important weeds in the mangrove ecosystem. Besides, Sesuvium portulacastrum, Suaeda nudiflora, Salicornia brachiata, Sarcolobus carinatus, Heliotropium curassavicum, and Ipomoea pes-caprae were also distributed widely in this region. The frequency, density, and abundance of parasitic and non-plastic weed flora in the study area were recorded to understand their habitat and impact on ecological equilibrium in the mangrove ecosystem.