Co/Mg/Al hydrotalcite-type catalysts have been loaded onto ceramic honeycombs and tested in the ethanol steam reforming (ESR) reaction for producing hydrogen under practical conditions. In contrast with previously reported cobalt-based systems, the formation of carbon was scarce. This has been ascribed to the unique formation of traces of metallic cobalt particles under reaction conditions, as inferred from HRTEM, magnetic measurements, and in situ X-ray photoelectron spectroscopy (XPS) experiments. The best catalytic performance has been exhibited by the catalyst derived from the hydrotalcite with a Co:Mg:Al molar ratio of 1 : 2 : 1, where CoAl spinel and CoO strongly interacting with MgO phases have been identified.