Abstract: Objective: The aim of the study was to analyze the populations of macroalgal in relation to four seasons in Tamil Nadu, India. Methodology: Fortnightly replicate of marine macroalgae were collected from four Southern districts of Tamil Nadu, India for a period of 12 months continuously. More than 435 specimens were collected from Tamil Nadu coast from April, 2010-March, 2011. More number of genus (30) as well as species (64) was recorded during Southwest monsoon. Results: The genus Gracilaria dominated in South West monsoon (15.28%) followed by Ulva in winter (14.81%). Besides, Caulerpa scalpelliformis distributed in all season in more than 10%. Season specific macroalgae was observed in Tamil Nadu. For instance, Amphiroa anceps, Bryopsis plumose, Caulerpa scalpelliformis (equal proportions) in summer, Gracilaria corticata in both South West and North East monsoons and Caulerpa scalpelliformis in winter. Acanthophora spicifera, Enteromorpha compressa, Galoxaura marguata and Sarconema filiforme recorded only during South West monsoon. Hormophysa triquetra was recorded only at summar, whereas Hypnea musciformis during winter. Abiotic factors have not influence on the distribution of macroalgae in the study areas. Conclusion: Hence, it is recommended to study the influence of other factors like seawater physio-chemical parameters and nutrient concentrations on the population level of macroalgae in the study area. Further the data is very much useful for specific plant collectors for their research work.