A ternary mixed ligand Cu(II) complex, [Cu(L)(Phen)], was prepared from the reaction of (E)-N′-((2-hydroxynaphthalen-1-yl)methylene)acetohydrazide [HL], Cu(NO₃)₂.3H₂O and 1,10-Phenanthroline in 1:1:1 molar ratio. This complex was fully characterized using spectroscopic and physicochemical methods. The structure of the complex was determined by single crystal X-ray diffraction. The Cu(II) center is coordinated by two oxygen and one nitrogen donors of L²⁻ and nitrogen atoms of the heterocyclic group. Electrochemical studies of the Cu(II) complex showed shifts in the ligand peaks as well as the appearance of new peaks after complexation. The electrochemical behavior of the Cu(II) complex was also studied using cyclic voltammetry. According to biochemical investigation (MCF-7 cells viability), anticancer activity of [Cu(L)(Phen)] was higher than those of Cu(NO₃)₂.3H₂O, HL and 1,10-Phenanthroline.