Copper/nickel nanocatalysts with a unique morphology were prepared by thermal reduction of a perovskite LaNixCu1−xO3 precursor (x=1, 0.9, and 0.7). During thermal reduction, copper was first reduced and reacted with lanthanum to form metastable Cu5La and Cu13La. When the thermal reduction temperature was increased, the perovskite decomposed to Ni and La2O3, CuLa alloys disappeared, and Cu deposits on Ni nanoparticles were generated, thereby forming Cu/Ni nanocatalysts with hierarchical structures. Nanosized nickel, decorated with copper and supported on La2O3, could be produced at 520–550 °C. The steam reforming of ethanol was used as a model reaction to demonstrate the catalytic capability of the materials formed. The hierarchical structure of the Cu/Ni/La2O3 catalysts confers synergetic effects that greatly favor the dehydrogenation of ethanol and which break the CC bond to produce a higher yield of hydrogen at a low reaction temperature, whereas La2O3 provides the required stability during the reaction. The reaction at 290 °C achieved almost 100 % conversion with a hydrogen yield reaching 2.21 molH2 mol−1EtOH thus indicating that this special structural feature can achieve high activity for the SRE at low temperatures. The proposed synthesis of nanocatalysts appears to be a good way to generate oxide-supported hierarchically structured nanoparticles that can also be applied to other reactions catalyzed by a heterogeneous metal oxide system.