This study reports a facile approach for examining surface morphology transitions in semiconductor nanoparticles (NPs), with a focus on pristine and magnesium-doped cadmium oxide NPs. Mg-doped CdO NPs are synthesized via co-precipitation, and their composition, structure, and elemental distribution are analyzed through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectra, and X-ray photoelectron spectroscopy (XPS), along with optical characterization and impedance analysis. Doping with Mg2+ changes the morphology from rod-like to quasi-spherical, reduces the crystallite size, and impacts their structural and functional properties. Optical transmittance analysis revealed that Mg2+ doping resulted in a reduction of the band gap energy. Impedance spectroscopy demonstrates improved dielectric constant and electrical conductivity for Mg-doped CdO NPs. The Nyquist plots show grain effects and the equivalent circuit analysis corresponds to a R(CR)(CR) circuit. These advancements point to the potential of spherical Mg-doped CdO NPs in semiconductor applications due to their superior structural and functional characteristics.