Biosynthesis of nanoparticles employing microbes has emerged as an alternative method to complex chemical synthesis. In the present work evaluation of extracellular biosynthesis of silver nanoparticles (Ag NPs) by Pseudomonas fluorescens was investigated. The silver nanoparticles were characterized by means of UV-VIS spectroscopy, Fourier Transform Infrared (FTIR) and Atomic Force Microscopy (AFM). The UV-VIS spectroscopy showed an absorption peak at 420 nm which corresponds to the plasmon resonance of silver nanoparticles. The Fourier Transform Infrared Spectroscopy confirmed the presence of protein as the stabilizing agent surrounding the silver nanoparticles. Atomic Force Microscopy showed topographical image of irregular silver nanoparticles and the size is 85.46 nm. The Silver Bio-nanoparticles were evaluated for their antimicrobial activities against Staphylococcus aureus and Escherichia coli. The highest antimicrobial activities have been recorded against Staphylococcus aureus and for Escherichia coli lesser activitywas recorded.