Nanoparticles are abundant and usable in the medical field as an antibiotic. It has been found that metal oxide nanoparticles, such as Co3O4, are efficient against bacteria that are resistant to antibiotics. Escherichia and Staphylococcus bring on enteric sickness and other illnesses. This study used co-precipitation to create Co3O4 nanoparticles. SEM, X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used to analyze these oxide nanoparticles. The XRD pattern validated the Co3O4 crystalline match. SEM also showed the morphology of Co3O4 nanoparticles. As determined by X-rays, Co3O4 has an average diameter of around 37.08 nm. The Co3O4 nanoparticles were highly pure, showed by an energy-dispersive EDX pattern. Both on their own and in conjunction with cephalexin, these metal oxide nanoparticles demonstrated antibacterial efficacy against S. aureus and E. coli. These Co3O4 nanoparticles showed high growth inhibition compared with using cephalexin individually. These conclusions found that the presence of cephalexin with Co3O4 showed high growth inhibition. The antibacterial activity of Co3O4 nanoparticles should be subjected for further studies.