A wall-jet electrochemical quartz crystal microbalance (EQCM) has been used to study oxidation of Co(II)ethylenediamine species on copper electrode both in stationary solution and under flow-through conditions. The current of anodic copper dissolution has been found from EQCM data. Co(II) oxidation current has been calculated as the difference between the net current and that found from EQCM data. This allowed partial currents of simultaneous Co(II) oxidation and copper anodic dissolution to be extracted from the EQCM data. The rate of Co(II) oxidation has been found to increase with solution pH, convection of the solution, concentration of halide additives, and their nature in the sequence Cl- < Br- < I-. The mechanism of electro-oxidation of Co(II)-ethylenediamine complexes on copper electrode is discussed.