Abstract: Biosynthesis of silver nanoparticles (Ag NPs) has emerged as an important area is nanotechnology and biotechnology due to growing need to develop environmental benign technologies. Metallic nanoparticles are traditionally synthesized by wet chemical synthesis techniques where the chemicals used are quite often toxic and flammable. The present study deals with cost effective and environment friendly given synthesis from 1 mM AgNO3 solution through the sea weed extract of S. agardhii as reducing as well as capping agent. The nanoparticles were characterized by surface plasmon absorbance measuring 409 nm. Scanning electron microscopy showed the formation of (Ag NPs) in the range of 40-50 nm and X-ray diffraction analysis of the freeze-dried powder confirmed the formation of metallic (Ag NPs). This study may be used in the development of value-added products from the sea weed for biomedical and nanotechnology based industries.