The nanocrystalline Mg_0.5Zn_{0.5_x}Co_xFe₂O₄ (x=0, 0.1,0.2,0.3,0.4 and 0.5) ferrites have been synthesized by sol–gel auto ignition method. Rietveld refinement of X-ray diffraction (XRD) patterns of all concentrations show mixed cubic spinel structure. The lattice constant values infer decreasing trend from 8.420 to 8.392Å with the substitution of Co²⁺. The crystallite size calculated from Scherer formula lies in the range between 28 and 37 nm which confirms the nano crystalline nature of synthesized samples. In order to study themorphology and phase structure of the synthesized samples, samples were examined by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) confirmed the homogeneous and well defined surface morphology of the synthesized samples. The elemental analysis as obtained from energy dispersive X-ray (EDAX) is in close agreement with the expected composition from the stoichiometry of reactant solutions used. The valence states of the Co²⁺ ions have been confirmed with the help of X-ray photo electron spectroscopy. Magnetization results obtained from the vibrating sample magneto meter (VSM) confirm that the substitution of Co²⁺ for Zn²⁺ caused an increase in the saturation magnetization and coercivity. The dependence of Mössbauer parameters, viz., line width, isomer shift, quadrupole splitting and hyperfine magnetic field on Co²⁺ substitution have been analyzed. Cation distribution estimated from XRD and Mössbauer spectroscopy are in good agreement with each other. The frequency dependent dielectric properties were studied by measuring dielectric constant (ε') and acconductivity (σ_ac) at 300K in the frequency range of 50Hz–5 MHz. The highest value for ε' and σ_ac is observed for x=0.5.