The YBa 2 Cu 3 O 7 nano/microsized single crystallites with spherical and rod-like morphologies were fabricated hydrothermally. The catalytic performance of the materials was evaluated for methane combustion. It is shown that there was a clear relationship between the a-oxygen desorption or initial H 2 consumption rate and catalytic activity. The single-crystalline perovskite-like cuprate catalysts outperformed the polycrystalline counterpart. The good catalytic performance of the hydrothermally derived YBa 2 Cu 3 O 7 single crystallites is associated with more a-oxygen adspecies, better low-temperature reducibility, high-quality single crystallinity, and unique morphology.