In this study the Mn1–2xZrxFe2−yNiyO4 nanoparticles fabricated by co-precipitation technique were investigated. Thermo-gravimetric analysis (TGA) exhibited the annealing temperature of the nanoparticles ~990°C. Cubic spinel structure of Mn1–2xZrxFe2−yNiyO4 nanoparticles was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. Crystallite size was calculated by XRD data and found in the range of 32–58nm. Photocatalytic activity of Mn0.92Zr0.04Fe1.88Ni0.12O4/graphene nanocomposites was tested by degrading methylene blue (MB) under visible light irradiation. The MB was almost completely degraded in the presence of Mn0.92Zr0.04Fe1.88Ni0.12O4-graphene nanocomposites under visible light irradiation. Dielectric parameters were also investigated in the frequency range 1×106–3×109Hz. An overall decrease in the values of dielectric constant, dielectric loss and tangent loss was observed on account of the substitution of Zr and Ni with Mn and Fe cations.