Shift from conventional (integrated) to organic system of nutrient management influences the weed spectrum and species richness. Weed communities in conventionally and organically managed cashew plots were studied to assess phytosociological parameters and community diversity indices. The weed spectrum was found to have widened considerably in both systems in comparison to weed species recorded thirty years back, and was dominated by broad-leaved and grass species. Species richness was slightly lower in the organically managed plots. In both systems, broad-leaved weeds dominated, accounting for more than 78% of the population. The major broad-leaved species were Synedrella nodiflora, Borreria hispida and Pouzolzia zeylanica, while the major grass species were Oplismenus burmannii, Brachiaria sp. and Panicum sp. Community diversity indices, viz. Simpson’s diversity index and evenness index, did not vary greatly between the two systems, indicating the uniformity of distribution of species, and lack of any major dominant species due to introduction in any one system alone