Codeposition of copper and molybdenum was obtained by electroplating using CuSO 4 and Na 2 MoO 4 with trisodium citrate as complexing agent. The molybdenum content which was investigated by inductively coupled plasma atomic emission spectroscopy in electroplated Cu-Mo increased, from 0.5 to 7.1 wt%, with decreasing current density in the range from 0.1 to 1.2 A/dm 2 during electroplating. X-ray diffraction showed that the structure of molybdenum is amorphous, and higher molybdenum content gave smaller and wider Cu (111) peaks, furthermore, made the surface morphology smoother. These suggest that molybdenum atoms are introduced into copper crystal lattices, resulting in breaking copper crystal lattices.