The biological synthesis of nanoparticles emerges as an eco-friendly and exciting approach in the field of nanotechnology. In the present investigation, we report the extracellular biosynthesis of silver nanoparticles (AgNP`s) using plant leaf extracts (Artocarpus heterophyllus) for the reduction of aqueous Ag+ ions and its increased antimicrobial activity. Stable silver nanoparticles were formed by treating aqueous solution of AgNO3 with the plant leaf extracts as reducing agent for reduction of Ag+ ions .The quantitative formation of synthesized nanoparticles monitored by UV-visible spectroscopy. After the characterization, these nanoparticles are evaluated for increasing the antimicrobial activities of different antibiotics against clinically isolated organism. The antibacterial activities of Vancomycin, Amoxyclav and Tetracycline increased in the presence of Ag- NPs against Salmonella paratyphi. Norfloxacin,Ciprofloxacin and Erythromycin antibacterial activities increased in the presence of Ag- NPs against Klebsiella pneumonia.