We report, here a simple green method for the preparation of silver nanoparticles (AgNPs) using the plant extract of Cleistanthus collinus as potential phyto reducer. The synthesized AgNPs were characterized by UV vis spectra, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results confirmed that the AgNPs were crystalline in nature and the morphological studies reveal the spherical shape of AgNPs with size ranging from 20 to 40 nm. The in vitro antioxidant activity of AgNPs showed a significant effect on scavenging of free radicals. The cytotoxicity study exhibited a dose-dependent effect against human lung cancer cells (A549) and normal cells (HBL-100), the inhibitory concentration (IC50) were found to be 30 mu g/mL and 60 mu g/mL respectively. The in vivo histopathology of mouse organs proved that AgNPs does not possess toxic effect and can be extensively applied in biomedical sciences. (C) 2013 Elsevier Ltd. All rights reserved.