The structural, optical, photocatalytic and dielectric properties of Cd_0.40Mn_0.60ZnO₂ annealed nanocomposites prepared by Hydrothermal and subsequently annealed at temperatures between 200 °C and 600 °C. The particle size, crystallite size, and inter-plane separation were all enlarged with increased T_ann at 600 °C and electrical dielectric loss increased. The specific surface area and photocatalytic activity were maximized, obtaining in this case a rate of degradation of 2 × 10^-4s^-1 at 400 °C. The lowest band gap = 1.55 eV was observed at 400 °C signifying enhanced optical absorption. The optical and dielectric properties exhibited a non-monotonic behavior: absorbance, optical dielectric loss, carrier density, dielectric constant, ac conductivity and Fill-factor, increased to the maximum values at 300 °C followed by a decrease. The dielectric constant (3.22), single and dispersion energies (10.58 eV …