A TiO2 photocatalyst modified with g-C3N4 and different wt% of CuO, is performed via hydrothermal method. The structural, morphological and spectroscopic characterizations are carried out. The ternary composite, g-C3N4/CuO/TiO2, exhibits greater photocatalytic activity than CuO/TiO2. The highest degradation of Levofloxacin reaches 99% and 44%, after 10 and 60 min UV irradiation over ternary and binary composites for 20 wt% of CuO, respectively, with a concentration of 5.10−3 g/L of LEVO and a photocatalyst mass of 2.10−2 g. The stability of g-C3N4/CuO/TiO2 is confirmed allowing its reuse for five successive cycles with a longer treatment time. Under solar irradiation, the degradation yield of Levo using g-C3N4/CuO/TiO2 is 100% after only 20 min. The as-synthesized nanocomposite present interesting electrochemical properties. In the medium-frequency region, the diameter of the semicircle for the g-C3N4/CuO/TiO2 electrode is much smaller than that of the CuO/TiO2 electrode, indicating a lower charge-transfer resistance.