Magnesium oxide nanoparticles (MgO NPs) have recently attracted significant interest due to their low human toxicity, potential antibacterial properties, excellent thermal stability, biocompatibility, and cost-effectiveness. However, their bioavailability in target cells is decreased by their restricted membrane permeability, hindering their potential as sustainable medicines. To address this issue, we suggest magnesium oxide nanoparticles doped with cerium (MgOCeNPs) as a promising alternative. This study compares the membrane permeability and antibacterial activity of MgOCeNPs with pure MgO nanoparticles. Various spectroscopic and microscopic techniques were used to analyze both types of nanoparticles. X-ray diffraction revealed lattice patterns in the doped nanoparticles, while Atomic Force Microscopy provided details on their height and three-dimensional (3D) structure. Ce doping does not alter the crystal structure of MgO (FCC), but it significantly affects microstructural characteristics such as lattice parameters, crystallite size and biological activity. The antimicrobial efficacy of MgOCeNPs was tested against the pathogenic bacteria E. coli and P. aeruginosa and the fungal strain THY-1. MgOCeNPs showed strong antibacterial and antifungal activity, evidenced by increased zones of inhibition, a shorter growth curve, a lower minimum inhibitory concentration (MIC₅₀), and enhanced cytotoxicity. Growth curve analysis revealed early and extended stationary phases and an earlier decline in the log phase. Large Unilamellar Vesicles (LUVs), in conjunction with the egg-phosphatidylcholine model, demonstrated dose-dependent cytotoxicity, increased production of intracellular reactive oxygen species (ROS), and membrane perforation. The observed membranolytic activity and ROS generation suggest that MgOCeNPs cause cytotoxicity through oxidative stress. These results highlight MgOCeNPs as a novel and highly effective antibacterial agent with significant potential for managing and treating various microorganisms.