During the present study, the biosynthesis of silver nanoparticles was made by using the filamentous fungus, Penicillium citrinum isolated from the soil sample of an industrial area of Chennai, Tamil Nadu, India. Fungal biomass was aerobically grown and fungal cell filtrate was challenged with1mM of AgNo3 resulted in the change of color solution indicated the formation of silver nanoparticles. These nanoparticles were confirmed by UVSpectrophotometric analysis and further analyzed by AFM study, which determined the particle size and average roughness. X ray diffraction (XRD) analysis determined the metallic nature of silver nanoparticles. The synthesized silver nanoparticles were checked for antibacterial efficacy alone and along with Ciprofloxacin which showed that these nanoparticles enhanced the antimicrobial activity of Ciprofloxacin against some bacterial pathogens.