Green nanotechnology, the science that utilizes the various plant resources for the synthesis of nanoparticles without posing any chemical hazards is proved to be an efficient application in conservation of energy and environment. In the present study, we report biosynthesis of silver nanoparticles using silver nitrate and the leaves extract of the plant Justicia adhatoda which acts as a reducing agent. Formation of nanoparticles was indicated by a color change from pale yellow to reddish brown. Characterization studies were done using UVSpectrophotometer and FTIR. A peak at 460 nm was obtained, confirming the formation of silver nanoparticles. The Scanning Electron Microscopy and Transmission Electron Microscopy studies revealed that the formed silver nanoparticles were spherical in shape with a smooth morphology and maximum number of particles was within the size range of 11nm- 20nm. The antibacterial activity of the synthesized silver nanoparticles was studied against different bacterial species and was found to be highly toxic.