The algae associated with mangroves is described. Substrate plays very important role in algal establishment in intertidal and subtidal areas. Algae colonising the mud surface are seasonal because of the unstable conditions causEd. by the erosion and accretion. Mud surface harbours unicellular algae. Multicellular algae was dominatEd. by blue-green form on the mud surface. The benthic algae of the mud surface are representEd. by the green filamentous Enteromorpha clathrate, Rhizoclonium sp. and thalloid Monostroma sp. etc. These algae were found to be growing in extreme conditions in the salinity range from 30-40 ppt, temperature and nutrients and high light intensity. Sometimes due to the strong cyclonic winds, algae growing in the nearby rocky area are uprooted and enter the mangrove area. The epiphytic algal flora on mangrove trunks, pneumatophores, stilt roots, upper branches and canopies are comparatively poor. With regard to biotic factors there are a number of animals grazing on mangrove associated algal species. Mangrove habitat as a whole is unfavourable for the growth of algal species because of the lack of stable substrate, high turbidity and physiological stress