The adsorption of the Ni(II) dimethylglyoxime complex, Ni(DMGH)(2), on mercury was studied as a function of time by voltammetric and differential capacitance methods in ammonia and berate buffers. The influence of the adsorption potential and the complex concentration was also studied. The adsorption equilibrium shows a reversible behaviour. The experimental data conform to the Frumkin adsorption isotherm. The standard electrochemical Gibbs energy of adsorption and the interaction parameter obtained from the fit indicate the presence of attractive forces between adsorbed molecules and a standard electrochemical Gibbs energy of adsorption comparable with those of pentanol and hexanol. The experimental rate of adsorption, at short times, is independent of time. It is also linearly dependent on the complex concentration and exponentially dependent on the adsorption potential. The experimental rate law can be explained with a model considering the adsorption kinetics as being controlled by the adsorption of the complex.