Silver nanoparticles (AgNPs) find a wide range of use in many fields, and the biosynthesis of AgNPs via biological routines has recently gained currency. In this study, Bacillus licheniformis TT01 strain was isolated from quail feces collected in Vietnam and evaluated for its ability to synthesize AgNPs. Through visual confirmation and ultraviolet and visible (UV–Vis) spectrum analysis, we found that the biosynthesis of AgNPs was realized in the process in which biomass of B. licheniformis TT01 was incubated with AgNO₃ solution. Obtained AgNPs were then assayed for antibacterial activity against three species of bacteria, namely Escherichia coli, Bacillus cereus and Ralstoniasolanacearum, showing better inhibitory action than the AgNO₃ solution and the bacterial extracellular fluid. The minimum inhibitory concentration (MIC) of AgNP solution was 206 ppm against E. coli and R. solanacearum and 343.3 against B. cereus. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the obtained AgNPs had a spherical shape and sizes ranging from 2 to 22 nm, in which particles from 2 to 10 nm appeared with the highest frequency.