The Dual Membrane Cell (DM-Cell) is an innovative concept for solid state fuel cells operating in the temperature range 600-700 degrees C. It is based on a junction between the cathode/electrolyte part of a Solid Oxide Fuel Cell (SOFC) and the anode/electrolyte part of a protonic SOFC (PCFC) via a mixed H+ and O2- conducting porous ceramic membrane, named Dual Membrane (DM). This Dual Membrane is the key feature of the DM-Cell architecture and constitutes a third independent gas compartment for water formation and evacuation. This innovation is expected to reduce the drawbacks associated to the presence of water at one or the other electrodes taking place in conventional SOFC and PCFC. The proof of the DM-Cell concept was obtained by several dedicated experiments, i.e. through the electrical characterization of complete cells in a three-compartments rig, specifically designed to detect water vapor formation in the DM compartment. The paper reports the proof of the concept of the DM-Cell through a set of electrochemical results performed on thick model cells. The applicability of a potentially industrial shaping process to this new design is demonstrated on plasma sprayed metal supported complete dual membrane cell. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.051304jes] All rights reserved.