This chapter highlights succinic acid mediated facile sonochemical method for synthesis of Mg-doped ZnO nanoparticles. The incorporation of Mg into ZnO matrix was investigated using X-ray diffraction (XRD) technique. Textural properties of as-synthesized undoped and Mg-doped ZnO samples were investigated using FESEM coupled with elemental mapping. Optical property investigations revealed that as the Mg-doping content increased up to 0.09%, the absorption edge slightly shifted to shorter wavelengths. Further increase in Mg-doping concentration (i.e., for 0.12%) experienced a shift toward higher wavelength. Additionally, reduced near band edge emission (NBE) and excitonic emission intensities were observed for the most active photocatalyst compared to undoped ZnO. Mg-doped ZnO (0.09 at%) nanoparticles (NPs) exhibited highest photocatalytic activity among all the synthesized samples and can degrade the methylene blue (MB) dye solution in merely 60 min under sunlight irradiation.