A hybrid membrane system composed of two insoluble cation-exchange membranes (Nafion) and a liquid membrane in between was studied. A series of organic and aqueous liquid membranes containing soluble polymers as macromolecular ionophores (macroionophores) was prepared and tested. The pertraction (membrane-transport) characteristics of poly(ethylene glycol) and its ionizable derivatives, including as poly[poly(oxyethylene) phosphate] (PPOEP) and di-[omega-methoxy poly(oxyethylene)] phosphate, were measured and are discussed as dependent on the composition and molecular mass of a macroionophore. The liquid membrane composed of PPOEPs dissolved in dichloroethane combined the cation-exchange properties with neutral coordination functionalities introduced by the poly(oxyethylene) backbone of this ionophore. The overall fluxes, facilitation factors, and the membrane system selectivity were measured in the carrier-mediated pertraction of transient metal cations (Cu2+, Zn2+, Mn2+, Co2+, and Ni2+). PPOEP could facilitate the pertraction of Zn2+ and Cu2+ over Ni2+ and Co2+. In the case of an aquatic hybrid membrane system, high but nonselective ionic fluxes were observed.