Zooplankton samples collected from ten stations covering the entire stretch of the Kadalundi-Vallikunnu CommunityReserve, Kerala, south India, for a period from July 2018 to June 2019 were studied. Twenty eight groups of zooplankton viz. copepods, foraminifera, medusae, chaetognaths, siphonophores, ctenophores, ostracods, cladocera, Lucifer sp., amphipods, isopods, appendicularia, Balanus nauplii, cyphonautes larvae, polychaete larvae, echinoderm larvae, ephyra larvae, brachiopod larvae, alima larvae of squilla, aquatic insect larvae, prawn larvae, crab zoea, crab megalopa larvae, bivalve larvae, pteropods, gastropod larvae, fish eggs and fish larvae were recorded. Among these, copepods formed the major portion of 43%. An average of 18330 nos. per 100 m3 was noticed from the study area. The maximum and minimum density of zooplankton was observed at Station 1 and 10 respectively and a decreasing trend in abundance was recorded from barmouth towards upstream stations. Seasonal studies indicated a maximum of 52% during pre-monsoon, followed by 36% during post-monsoon and a minimum of 12% during monsoon. Different indices of diversity, dominance plot, dendrogram and Multi Dimensional Scaling (MDS) plot are presented and discussed. Keywords: Biodiversity, Estuary, PRIMER, Primary consumers, Seasonality