In recent years, metal oxide nanoparticles have attracted considerable attention in various scientific and technological fields due to their unique physicochemical properties. In this study, MgO and CuO metal oxide nanoparticles were synthesized via a green synthesis approach using Verbascum extract, and their structural, chemical, and biological properties were investigated. XRD analysis confirmed the successful synthesis of MgO and CuO nanoparticles with crystallinity percentages of 63.5% and 39.1%, respectively. The crystallite sizes were estimated to be approximately 14 and 21 nm for MgO and CuO, respectively. FTIR spectra verified the presence of characteristic Mg-O and Cu-O bonds. FESEM images revealed that MgO nanoparticles exhibited a dense nanorod/nanoneedle morphology with diameters ranging from approximately 50 to 150 nm and lengths of 300 to 800 nm. In contrast, CuO nanoparticles displayed a three-dimensional porous sponge-like structure with interconnected pores in the range of 200 to 800 nm. EDS analysis further confirmed the high purity of the synthesized nanoparticles. Antibacterial evaluation demonstrated that both nanoparticles exhibited identical MIC and MBC values of 270 µg/mL against the Gram-negative bacterium Escherichia coli, indicating the need for relatively high concentrations to inhibit the bacterium. In contrast, significantly stronger antibacterial activity was observed against the Gram-positive bacterium Staphylococcus aureus. MgO nanoparticles showed MIC and MBC values of 135 µg/mL, while CuO nanoparticles exhibited the highest antibacterial efficacy with MIC = MBC = 33.75 µg/mL, resulting in complete inhibition of S. aureus. These findings indicate the superior antibacterial performance of CuO nanoparticles compared with MgO, which may be attributed to their porous structure and higher active surface area, enhancing their antimicrobial effectiveness.