Spatial and temporal variations in the distribution of plankton of a tropical reservoir were investigated for six months.  Chlorophyceae was richest in the phytoplankton community in terms of the number of species and individuals. They were more abundant in the late rainy /early dry season with Pediastrum simplex and Coelastrum chodati being the dominant species. Constant species occurred only in Chlorophyceae which included Spirogyra, Closterium sp., Coelastrum chodati, Pediastrum simplex, Ulothrix zonata and Scenedesmus quadricauda. Cyanophyceae developed mainly in the late dry season months (reached peak in March) with Microcystis flos-aqua being dominant. In the zooplankton community, Crustacea had the highest number of individuals and were more abundant in the late dry season. Camptocercus sp., Bosmina sp., and Daphnia magna were the main species. Rotifers had the highest species number with peaks observed in the late rainy/early dry season. The common species encountered included Chromagaster sp., Epiphanes sp., Gastropus sp., Nolthoca sp., Trichocerca sp., and Brachionus sp. The common protozoan species were Ichthyophthrius, Chilodonella, Prorodon, and Colpoda. The diversity indices calculated varied spatially; phytoplanktonic organisms were more diverse in Station 1 with the least evenness, highest evenness occurred in Station 2. The increase in the total number of taxa encountered in this study compared to previous studies and the implication of Microcystis flos-aqua being the dominant blue-green algae were discussed.