The seaweeds viz., Ulva reticulata, Ulva lactuca, Caulerpa racemosa, Hypnea musciformis, Hypnea valentiae, Gracilaria corticata, Gracilaria edulis, Gelidiella acerosa, Sargassum myriocystum and Padina gymnospora were collected from Mandapam coast of Tamil Nadu, India. The seaweed extracts were prepared by using various solvents viz., methanol, acetone, chloroform, hexane and ethyl acetate by Soxhlet apparatus. The extracts were evaporated to dryness and stored in a refrigerator for future use. The antibacterial and antifungal activity of the seaweed extracts were determined by disc diffusion method and the minimum inhibitory concentration of the extracts were tested by broth dilution method. The Ampicillin (5 µg/ml) and Flucanozole (100 units/disc) were used as positive controls for bacteria and fungi respectively. The disc containing 5% DMSO alone used as blind control. Among the ten seaweeds tested, the highest mean zone of inhibition was observed in methanol extract of Gracilaria corticata against all tested microbial pathogens and the highest minimum inhibitory concentration was obtained in methanol extract of Gracilaria corticata against all tested bacteria and fungi.