Magnesium-doped cadmium ferrite nanoparticles, Mg_XCd_1−XFe₂O₄ (where, X = 0, 0.2, 0.4, 0.6, 0.8, 1) were synthesized by a combustion method using curd as fuel. The synthesized nanoparticles were characterized using XRD, FTIR, SEM, HRTEM, XPS, PL and UV-VIS spectroscopy. XRD studies reveal that the synthesized nanoparticles exhibit a cubic spinel structure, and the average crystalline size and lattice parameters decrease with the increase in magnesium doping. The vibrational stretching modes of the octahedral and tetrahedral sites were confirmed by FTIR, and the agglomerated and nanoflake-like structure was confirmed by SEM and HRTEM. The elemental composition and oxidation and transition states of the synthesized nanoparticles were revealed by X-ray photoelectron spectroscopy. Luminescence spectroscopy reveals that the luminescence intensity decreases with the increase in magnesium doping. From the UV-VIS spectroscopy, the band gap of the synthesized nanoparticles is determined, which decreases as the magnesium doping increases. The photodegradation capabilities of the synthesized nanoparticles were assessed for the degradation of malachite green dye, under visible light irradiation. Electrochemical studies reveal that the synthesized nanoparticles show appreciable electrochemical performance. Pure CdFe₂O₄ and Mg-doped CdFe₂O₄ were inspected against the Gram-positive bacteria S. aureus and Gram-negative bacteria Shigella, and it was found that the antibacterial activity improved with magnesium doping compared to the pure CdFe₂O₄ nanoparticles.