A novel perovskite ceramic based on crystalline structure of ACu3Ti4O12 compound, is presented. Ti-sites were occupied by ∼50 at.% of Ta5+, and A-sites remained vacant, leading a formation of Cu3Ti2Ta2O12. This ceramic exhibited a high ε′ value in a low frequency range at room temperature. The high-frequency dielectric relaxation behavior showed activation energies of 0.146 eV. Valence states of Cu and Ti cations (i.e., Cu+, Cu3+ and Ti3+) in Cu3Ti2Ta2O12 ceramic were investigated using X-ray photoelectron spectroscopy. Impedance spectroscopy analysis revealed that Cu3Ti2Ta2O12 was electrically heterogeneous and comprised of semiconducting grains and insulating grain boundaries. Maxwell-Wagner polarization related to internal barrier layer capacitor model was suggested to be the origin of this high dielectric response.