Nanotechnology deals with the Nanoparticles having a size of 1-100 nm in one dimension used significantly concerning medical chemistry, atomic physics, and all other known fields. These particles can be prepared easily by different physical, chemical and biological approaches. But the biological approach is the most emerging approach of preparation because this method is easier than the other methods, eco-friendly and less time consuming. In this study green synthesis of silver nanoparticles (AgNPs) of Ziziphus nummularia (ZN) was done using the magnetic stirrer method. These AgNPs were characterized by UV-vis Spectroscopy, FTIR and SEM technique and the optimization was done by varying the root extract volume, silver nitrate concentrations, pH and temperature. It was observed that ZN extract can reduce the silver ions in to AgNPs with in 30 min of reaction time. The surface plasmon resonance peak observed near 430 nm, confirmed the reduction of Ag+ to Ag0 . Maximum absorbance peak 430 nm was observed with 2mM AgNO3 solution with standard condition of 9pH and 70°C temp. at magnetic stirrer followed by 42 hrs incubation during the optimization of stable AgNPs. SEM images clearly shows that synthesized AgNPs are in spherical shape with size range 20-50 nm. FTIR clearly indicating the presence of capping and reducing agents around the AgNPs synthesised from crude extract of ZN. The biosynthesized AgNPs exhibited significant antimicrobial activity against pathogenic Staphylococcus aureus, Enterococcus faecalis (a Gram-positive bacterium), Pseudomonas aeruginosa and Escherichia coli (a gram negative bacterium) and Aspergillus niger (plant pathogenic fungal strain), Candida albicans (human pathogenic fungal strain). This novel approach of bionanotechnology can be taken up by the researcher in near future to develop the effective bionaomedicine, biopesticides, nanofood composites etc.