The effect accompanying anion on the transport of Ni2+ and competitive transport of Ni2+ and Fe3+ ions through charged polysulfone or polysulfone polyester-supported cation exchange membranes was studied under Donnan dialysis conditions. In the Donnan dialysis process, two electrolyte solutions were separated by ion permeable membrane, the one side (feed solution) initially containing metal salts or their mixtures, the other is HCl and no external potential field is applied. The transport of metal ions through membranes was correlated with the efficiency factor (EF) values as well as with fluxes and depended on the interaction between the fixed groups in the membrane and the metal ions. The EF value of Ni2+ as a single as well as mixture state was higher than that of Fe3+ for both types of membranes. The effect of accompanying anion on the transport of Ni2+ was found to be in the following order of Cl- > NO3- > SO4-2, and the results were correlated with the EF values, as well as with the membrane structure.