Biosynthesis of nanoparticles is considered a new approach of research in nanotechnology that has recently gained immense interest worldwide. Biologically synthesized silver nanoparticles (AgNPs) are being fashionably widely used particularly in the medical field. In the current investigation, the green chemistry of silver nanoparticles synthesis from the aqueous solution of silver nitrate as a rapid, feasible and eco-friendly technique was described. Extracellular biosynthesis of silver nanoparticles was carried out using bio-extracts of Ziziphus spina-christi leaves for the reduction of aqueous silver ions in a short period. The silver nanoparticles formation was detected by the colour change of bio-extracts and further confirmed with the help of UV-VIS spectroscopy where the peak values were in the range of 415-420 nm. In this study the aqueous extract and silver nanoparticles phytosynthesized by Ziziphus spina-christi leaves was tested for its antibacterial activity using agar well diffusion method against bacterial species: Pseudomonas aeruginosa, Bacillus subtili, and Staphyllococcus aureus. Our results showed that, the inhibition zone ranged between (15 ± 1.08 – 20 ± 0.9 mm) for AgNPs mediated by Ziziphus spina-christi leavesagainst tested bacteria. Furthermore, P.aeruginosa displayed the highest zone of inhibition compared with others. The observed differences between the bactericidal activities of AgNPs against the tested microorganisms might be attributed to the type of bacterial species treated in this study. Our findings indicated that silver nanoparticles synthesis mediated Ziziphus spina-christi leaf extract has an efficient bactericidal activity against the bacterial species tested. However, the aqueous extract showed no inhibition zone. It would really be a challenging task in the future investigations to perform experiments at a molecular level to explore the unknown mechanism whereby AgNPs are biologically synthesized. Answers to such mysterious questions will open further avenues to gain deeper insight for better understanding of the potential role of bio-extract in silver nanoparticles formation.