This study was concerned with the isolation of bacterial strains from different water sources. Among these strains; Enterobacter sp. exhibited extracellularly biosynthesized silver nanoparticles with good monodispersity. Enterobacter sp. has produced extremely stable nanoparticles within 72 hrs at 35°C in dark conditions. These nanoparticles are characterized by UV–vis spectrophotometer, transmission electron microscopy, Zeta potential analyzer, and size distribution by volume. Enterobacter sp. synthesized 9.45-17.15 nm sized spherical shaped silver nanoparticles. The presence and binding of stabilized proteins with nanoparticles were confirmed by the zeta size distribution by volume. Our study demonstrates that silver nanoparticles are potent inhibitors of the plant pathogenic fungus, Fusarium oxysporum f. sp. lycopersici.