Nanocrystalline nickel-molybdenum (Ni-Mo) alloy thin films and nanowires array were synthesized in acidic aqueous solution containing citric acid using an induced co-deposition technique. Cross-sectional scanning ion microscope (SIM) images of the electrodeposits revealed that pure Ni consists of large crystal grains with diameter of several mu m, while Ni-4.5%Mo alloy consists of columnar crystals with diameter of several hundred nm and long axis of the columnar crystals was arrayed vertically to the film plane. On the other hand, no crystal grains were found in Ni-23.6%Mo alloy which was composed of an amorphous phase. Electrodeposited pure Ni thin film was hardly magnetized in perpendicular direction to the film plane, while the magnetization of nanocrystalline Ni-11%Mo alloy thin film reached to saturation at ca. 2.5 kOe. On the contrary, Ni nanowires array was easily magnetized in perpendicular direction to the membrane film plane which corresponds to the long axis direction of nanowires, while the nanocrystalline Ni-8.4%Mo alloy nanowires array was magnetized isotropically in both direction and the soft magnetic property was improved with increasing Mo content in the electrodeposits. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.013210jes] All rights reserved.