Nanotechnology and nanoparticles (NPs) researches have attracted a lot of interest in recent decades, and there is growing attention to find more effective ways for their synthesis. The use of biological approach, (using various microorganisms), as bio-nanofactories provides a clean and promising alternative process for the fabrication of silver nanoparticles. This study confirmed the production of silver nanoparticles (AgNPs) by a cost effective, safe and environment-friendly technique using silver nitrate and supernatants of the bacterium Bacillus subtilis ssp spizizenii MT5 as a bio reducing agent. Supernatants of the tested microbe growing on nutrient broth (NB) were used for fabrication of AgNPs. Some parameters of optimization i.e., incubation time, silver nitrate concentration, mixing ratio of culture supernatant and silver nitrate, media type, temperature degree and pH level were studied. The biosynthesis of AgNPs in the cell extract filtrate was confirmed and characterized by biophysical methods using the advanced available instruments. The determined conditions for the bioinspired synthesis of AgNPs revealed that incubation time was 40 h, silver nitrate concentration was 3mM, supernatant and silver nitrate ratio was 1:4, medium type was nutrient broth (NB), agitation speed was 160 rpm, temperature degree was 35°C and pH level was 7. Characterizations of the produced bio silver nanoparticles were done using the advanced available methods. The ultraviolet-visible spectrum showed an absorption peak at 420 nm. Transmis­sion electron microscopy (TEM) showed that the mean diameter of the formed AgNPs was 38 to 49 nm. Powder X-ray diffraction (XRD) showed that the particles are crystalline in nature, with a face-centered spherical structure. Dynamic light scattering (DLS) and Zeta potential analysis showed that the average AgNPs size was 31.42 nm and the zeta potential was -20.8mV, Fourier Transform Infrared Spectroscopy analysis (FT - IR) confirmed the presence of elemental silver and the dual function of biomolecule responsible for the bio reduction and stabilization of AgNPs in the reaction mixtures. The scanning electron microscopy (SEM) micrograph indicated that produced AgNPs are spherical in shape. However, it also showed an indeterminate morphology. Energy-dispersive X-ray spectroscopy (EDX) exhibited strong signal in the silver region which confirms the formation of AgNPs.