Allium cepa extract was used to prepare AgO NPs, NiO NPs, NiO-AgO NCs by plant-mediated synthesis, all characteristics of these nanoparticles and antibacterial properties have been studied. XRD analysis confirmed the crystalline nature of the synthesized nanoparticles. The average crystalline size was 14.75nm, 38nm and 36.4 nm  for AgO NPs, NiO NPs and NiO-AgO NCs respectively. NiO NPs were hexagonal, while AgO NPs were monoclinic phase. The NiO-AgO NCs represents a hybrid structure composed of NiO NPs and AgO NPs phase. EDX analysis verified that all samples contained the elements that were present (O, Ni, and Ag). UV-Vis was used to calculate the AgO, NiO, and NiO-AgO energy gaps are 3.11 eV, 3.08 eV and 3.38 eV  respectively. Additionally, From FTIR spectroscopy, the investigation found that the extract from Allium cepa included functional groups that serve as agents that reducing and capping, the spectrum verifies existence of AgO and NiO and combination of AgO and NiO with adsorbed surface groups such carbonates and water Furthermore, from zeta potential, AgO NPs, NiO NPs and NiO-AgO NCs showed great stability at -29.1 mV, -22.6 mV, and -21.3 mV respectively. The study revealed that the material demonstrates greater antibacterial activity against Gram negative bacteria compared to Gram-positive ones. The NiO-AgO NCs showed the maximum inhibition values against E. coli and Staphylococcus aureus at a concentration of 75%, measuring about 28 mm and 27 mm, respectively