The seaweed Turbinaria conoides was collected from the east seashore of the south India. The dried seaweeds were converted into fine powder, mixed with acetone, and their antibacterial substance was extracted. The extracted substance was characterized by the use of Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy for functional group identification. The presence of bromine, amine, and phenolic groups was confirmed. Nanosized particles were confirmed by transmission electron microscopy studies. The extract was applied on the enzyme scoured and dyed cotton fabric for bioantibacterial finish. The antibacterial activity of extract on the finished fabric was confirmed by the test results. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2287-2292, 2009