Two types of Cs+ ion-selective crown ether Nafion composite membranes have been prepared. In one case, the dibenzo-21-crown-7 (DB21C7) has been incorporated uniformly in the Cs+ form of Nafion-117 membrane in varying molar ratio with respect to Cs+, and in the other case, Cs+ driven loading of DB21C7 has been confined (ion gating) to a very small thickness (25 pm) from one of the surfaces of the Nafion-117 membrane. The surface confinement of Cs+ in the ion-gated membrane has been studied by energy dispersive X-ray spectroscopy and secondary ion mass spectrometry. The cation (Cs+/Na+) transport properties of the membranes have been studied under application of electric field. In the uniformly crown-ether-loaded membranes (Cs-Naf-CR), the decrease in crown ether molar ratio has been found to increase the mobility of Cs+ through the membrane at the cost of mutual cationic selectivity (Cs+ over Na+). On the other hand, enhanced selectivity of Cs+ over Na+ with significant cationic transport at room temperature has been obtained with the ion-gated membrane (Cs-H-Naf-CR). When applied to the simulated nuclear waste solution, selective transport of Cs+ has also been obtained using this gated membrane even in the presence of very high Na+ (Cs+:Na+ = 1:1428) concentration in aqueous solution.