The excessive use of antibiotics led to the appearance of many strains of resistant bacteria, so it became necessary to use new antibacterial techniques. The aim of this work is the synthesis of novel core–shell NPs (NiO@ZnO) for antibacterial applications. A novel NiO@ZnO core–shell nanomaterial with a nanosize and uniform shape has been synthesised using the two-step pulsed laser ablation in liquid (PLAL) method. The first step is the laser ablation of the nickel target and the production of NiO NPs (core) colloidal, followed by the second step, the ablation of ZnO (shell) inside NiO NPs colloidal. The transmission electron microscopy results approve the formation of NiO@ZnO core–shell NPs with an average particle size of 54.4 nm for NiO particles and 60.7 nm for the NiO@ZnO core–shell. The antibacterial activity was examined against the pathogenic bacterial strains E. coli and S. aureus. We found that in the case of NiO, the inhibition rates were 62.4 and 59.2% for E. coli and S. aureus, respectively. While with NiO@ZnO NPs, this result was improved to 74.8% for E. coli and 71.2% for S. aureus. So, it was found that using the core–shell NPs increased the antibacterial activity of NPs, and the use of NiO NPs and core approved their effect as antibacterial agents due to their special properties. This behaviour is primarily because of the accumulation of the NiO@ZnO NPs on the surface of the bacteria, which leads to cytotoxic bacteria and a relatively increased ZnO, causing cell death. Furthermore, the use of a NiO@ZnO core–shell material will inhibit the bacteria from nourishing themselves on the culture medium. Therefore, core shelling metal oxides with another metal oxide or other material improves their antibacterial activity compared with using them alone.