Silver nanoparticles (AgNPs) have fascinated significant attention because of their wide range of biological and industrial applications. In this study, reports the synthesis, and assessment of the stability and antibacterial capability of silver nanoparticles (AgNPs) synthesized via sodium borohydride (NaBH₄) and stabilized by sodium dodecyl sulfate (SDS). AgNPs were prepared at varying silver nitrate (AgNO₃) concentrations (0.1, 0.2, 0.5, and 1.0 mM) and confirmed by UV-Vis spectroscopy, which revealed surface plasmon resonance (SPR) peaks ranging from 393 to 411 nm, depending on precursor concentration. The SPR intensity increased with both AgNO₃ concentration and temperature, with maximum absorbance values reaching 3.57 L•mol⁻¹•cm⁻¹ at 1.0 mM AgNO₃ and 100°C. Time-based stability tests showed that AgNPs retained optical stability for over 120 days, with minimal peak broadening and a slight red shift in λmax. pH-dependent studies revealed optimal stability at pH 7–8, while aggregation was observed at 1–2 pH and pH 13. Antibacterial assays against Escherichia coli demonstrated strong inhibition, with zones of inhibition increasing from 1 mm at 0.1 mM to 2 mm at 1.0 mM. The results confirm that AgNPs synthesized under optimized conditions are both stable and highly effective as antibacterial agents, supporting their potential application in nanomedicine and environmental disinfection.................... Keywords:............... Silver nanoparticles, UV-V Surface plasmon resonance, SDS stabilizer, Time and pH stability, Antibacterial, Escherichia coli.