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 research article we present a simple and eco-friendly biosynthesis of silver nanoparticles using Garcinia mangostana leaf extract as reducing agent. The aqueous silver ions when exposed to leaf extract were reduced and resulted in silver nanoparticles whose average size was 35nm. The silver nanoparticles were characterized by UV–Visible, Fourier transform infra-red spectroscopy (FT-IR) and transmission electron microscopy (TEM) techniques. Furthermore these biologically synthesized nanoparticles were found to be highly effective against different multi-drug resistant human pathogens.