Silver has been known since ancient history for its antimicrobial property. The silver nanoparticles were obtained by a green synthesis method in this study. Seaweeds were used as the bioreductant for the reduction of the silver salt to form the nanoparticles. The formation of the silver nanoparticles was confirmed with the dark brown colour development and it was characterised with UV-Visible spectroscopy. The Transmission electron micrographs indicate the size of the nanoparticles to be in the range of 25-40 nm and the nanoparticles were spherical in shape. The activity of the nanoparticles to inhibit the growth of bacteria was tested against a Gram positive Bacillus cereus and a Gram negative Escherichia coli. The silver nanoparticles exhibit good antimicrobial activity and hence their potential application in medicine as a wound dressing or for sterile clothing in hospital environment.