Copper ferrite (Cu_xFe_3-xO₄) thin films synthesized on α-Al₂O₃(0001) substrates exhibited the spinel structure for Cu compositions up to x = 1.0. The substituent Cu ions exhibited charge valence of +2, occupying both the tetrahedral and the octahedral sites of the spinel lattice. Magnetic hysteresis measurements on the Cu_xFe_3-xO₄ films revealed gradual loss of saturation magnetization (M_s) with increasing x: M_s is reduced to ~50% that of Fe₃O₄ for x = 1.0. The electrical resistivity (ρ) of the Cu_xFe_3-xO₄ films increased with x: ρ for x = 1.0 is larger by a factor of 30 than that of Fe₃O₄. The evolution of the magnetic and electrical properties of Cu_xFe_3-xO₄ can be explained in terms of the competition between the tetrahedral and octahedral Cu²⁺ density for ferrimagnetic moment and polaronic conduction.