A bio-fabrication approach is a novel way to develop chitosan-stabilized magnesium oxide nanomaterials (cMgO-NMs). The process involves utilizing polymeric chitosan as the reducing and stabilizing agent. The characteristics of the developed cMgO-NMs were determined using various spectroscopical techniques. Fourier-transform infrared spectroscopy (FTIR) analysis revealed crucial functional groups, Ultraviolet-visible spectroscopy (UV-Vis) spectrum showed nanomaterial development with a peak at 358 nm, and powder X-ray diffraction (PXRD) pattern confirmed a pure cubic crystalline structure. Field emission scanning electron microscopy (FE-SEM) images depicted spherical shape, while energy dispersive X-ray analysis (EDX) confirmed Mg presence. The photocatalytic efficacy of these nanomaterials in degrading dye methylene blue (MB) was examined, and the findings demonstrated the remarkable proficiency of cMgO-NMs in breaking down the dye. The cytotoxic effects of cMgO-NMs were assessed for the first time on PCI-9A and PCI-13 cancer cell lines, yielding an IC