Nanoparticles plays a key role in the development of novel antibacterial substances against various pathogenic microorganisms. These nanoparticles due to their smaller size could be very effective as they can improve the antibacterial activity through lysis of bacterial cell wall. In the present research work, ZnO, MgO, NiO, AlO nanoparticles, and Mg NiO, and Al ZnO composite oxides were synthesized by green method from Ocimum basilicum leaves extract. The nanoparticles formed were evaluated using FTIR, XRD, EDX, and SEM to confirm the formation of NPs and to determine the morphology, elemental composition, shape and size, composition, and nature of bonds present in the NPs. Further, the NPs were tested for their antibacterial activity. In particular, ZnO NPs showed a good inhibitory effect against Pseudomonas aeruginosa with 20 mm zone of inhibition. Hence, the process reported herein could be optimized for large-scale preparation of NPs. Research Highlights• Green synthesis of ZnO, MgO, NiO, AlO nanoparticles, and Mg NiO, and Al ZnO composite oxides using Ocimum basilicum leaves extract • NPs were characterized by various established characterization techniques like FTIR, XRD, EDX, and SEM.• NPs showed antibacterial activity which was investigated by agar well diffusion method against Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus.• The method proved to be very simple, cost-efficient, and convenient.