The electrodialysis of a 0.005 M copper(II) chloride solution simulating electroplating wastewater has been studied. Exceeding the limiting current on an MK-40 cation-exchange membrane leads to the precipitation of copper hydroxide on the membrane surface, which acidifies the solution in the concentration compartment by catalyzing the water dissociation reaction. It has been shown that an MA-40 membrane sorbs up to 15 wt % copper as a result of complexation with functional groups. During the electrodialysis at overlimiting currents, the MA-40 membrane becomes a source of protons to the desalting compartments and the membrane resistance increases because of the formation of copper hydroxide and/or oxide in large pores.