Oxyhydrides are promising compounds as supports for ammonia synthesis catalysts because they suppress hydrogen poisoning on the catalyst surface and enhance the ammonia synthesis activity. Herein, we developed a facile method for preparing BaTiO2.5H0.5, a perovskite oxyhydride, on a TiH2surfaceviathe conventional wet impregnation method using TiH2and Ba hydroxide. Scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscopy observations revealed that BaTiO2.5H0.5crystallized as nanoparticles ofca.100–200 nm on the TiH2surface. The Ru-loaded catalyst Ru/BaTiO2.5H0.5-TiH2exhibited 2.46 times higher ammonia synthesis activity (3.05 mmol-NH3g−1h−1at 400 °C) than the benchmark Ru catalyst Ru–Cs/MgO (1.24 mmol-NH3g−1h−1at 400 °C) because of the suppression of hydrogen poisoning. The analysis of reaction orders showed that the effect of suppressing hydrogen poisoning on Ru/BaTiO2.5H0.5-TiH2was equivalent to that of the reported Ru/BaTiO2.5H0.5catalyst, thus supporting the formation of BaTiO2.5H0.5perovskite oxyhydride. This study demonstrated that the selection of appropriate raw materials facilitates the formation of BaTiO2.5H0.5oxyhydride nanoparticles on the TiH2surface using the conventional synthesis method.