A green and rapid approach for synthesis of magnetite (Fe3O4) and silver (Ago) nanoparticles using plant leaf extracts of carob, olive, loquat and pistachio in a single-pot process at ambient temperature. The starting materials for synthesis magnetite and silver nanoparticles were ferrous chloride, ferric chloride and silver nitrate, respectively. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), UV-vis spectroscopy, Atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM). By changing the ratio of plant leaf extract to iron and silver ions and reaction time, the size of nanoparticles could be varied from 5 ± 1.2 to 20 ± 4.4 nm. FT-/IR spectra indicate that plant leaf extracts have been bound onto the surface of the nanoparticles. The antibacterial activity of biosynthesized silver nanoparticles showed effective inhibitory activity against water borne pathogens. This approach provides a facile, cost effective, eco-friendly and promising route to prepare magnetite and silver nanoparticles for the antibacterial activity, bio-sensing and Nano-electronic applications.