Abstract: The study area, Ratnagiri is situated at 170North and 730East and having an area of about 50,209 sq miles. The coastline of Ratnagiri district is 250 miles long and marked with several islands, which is a result of drowned topography. Ratnagiri coast has been blessed with luxuriant, thick mangrove vegetation with patches of other associated flora and fauna. Bhatye estuary is situated at 73015’ East and 16051’ North near Ratnagiri and known for the mangroves on the mud flats. Zooplankton samples were collected by surface hauling by using conical plankton net (80 µm bolting nylon). The zooplankton samples were then sorted out making sub-samples. The zooplanktons are the secondary producers and the first level converters of plant matter into animal substances and thus they occupy an important place in the food web of aquatic environments like mangroves. The zooplankton assume a great ecological significance in mangrove ecosystems as this ecosystem if the feeding, breeding and nursery grounds for many fin and shell fishes; and the young fin and shell fishes (meroplankton/larvae) spend most of their live times in the brackish waters, and after becoming adult they move over to sea. Hence, zooplankton determine the quantum of fish stock. The zooplankton species like Acrocalanus species, Eucalanus pileatus, Lucicatia flavicornis, Mesocyclops species and Pontellina plumata dominated the estuarine region.