The electrodeposition of the binary Ni-Mo alloys was investigated using different molar ratios of Ni:Mo, in a sodium citrate electrolyte at pH 4.0. Cyclic voltammetry was performed at different ion concentration ratios in order to determine their electrochemical behaviour. The deposit composition was determined by AAS. The electrodeposits were also analysed by SEM, EDS, XPS and XRD techniques. Voltammetric analysis of the deposits only presents dissolution peaks when high Ni ion concentrations are used. Chemical analysis of solutions obtained after dissolving the deposited films show that the reduction of the Ni and Mo occurs simultaneously over all the potential range studied and an induced process was observed for Ni:Mo ratios of 1:1 and 1:10. SEM micrographs revealed that the morphology is clearly altered when the nickel (II) concentration is increased, changing from fine-grained and smooth deposits to nodular and adherent ones. XPS measurements show that molybdenum species on the surface are probably a mixture of polyvalent molybdenum oxides or hydroxides (mainly in the form of the Mo(IV) and Mo(V)) and also metallic molybdenum.