There is an increasing commercial demand for nanoparticles due to their wide applicability in various areas such as electronics, catalysis, chemistry, energy, and medicine. Metallic nanoparticles are traditionally synthesized by wet chemical techniques, where the chemicals used are quite often toxic and flammable. In this work, we describe a cost effective and environment friendly technique for green synthesis of silver nanoparticles from 5mM AgNO3 solution through the extract of Argimone maxicana leaf as reducing agent as well as capping agent. Nanoparticles were characterized using UV-Vis absorption spectroscopy, FTIR, XRD and SEM. X-ray diffraction and SEM analysis showed the average particle size of 30 nm as well as revealed their structure. Further these biologically synthesized nanoparticles were found to be highly toxic against different bacterial spp. The most important outcome of this work will be the development of value-added products from Argimone maxicana (a potential weed of India) for biomedical and nanotechnology based industries. This is for the first time that Argimone maxicana weed leaf extract was used for the synthesis of nanoparticles. [ABSTRACT FROM AUTHOR]