The mechanical strength of thin, symmetric sandwich specimens consisting of a dense yttria-stabilized zirconia (YSZ) substrate coated with a porous NiO–YSZ layer at both major faces was investigated. Specimens were loaded in uniaxial tension to failure following heat treatments at various temperatures. In comparison with the YSZ material, the failure strength of coated specimens was found to increase for heat treatments at 1100°C, but decreased again with further increased heat-treatment temperatures.