Copper oxide (CuO) and zinc oxide (ZnO) nanoparticles were synthesized by Pterocarpus santalinus leaf extract following the green method as a reducing and capping agent. Analytical methods like scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy were followed for characterization of synthesized nanoparticles. Outcomes demonstrated that crystalline CuO and ZnO nanoparticles with distinct morphologies have successfully formed. The ability of metal oxide nanomaterials against the growth of Aspergillus niger fungus was tested by agar diffusion method on PDA plates. Pure culture of the isolated fungus from onions was used in this experiment. Fungal inoculum was prepared and spread on PDA plates and tested for growth inhibition with varying concentrations of CuO and ZnO nanoparticles using Disk Diffusion Method. A successful growth inhibition was identified in plates treated with CuO and ZnO.