The performance of yttrium-doped barium zirconate and cerate-based perovskite-type oxide supported ruthenium catalysts for the thermal catalytic NH3 synthesis process has been studied; these materials are expected to be applied as electrode catalysts for the electrochemical synthesis process of ammonia (NH3), namely, NH3 electrolysis. The BaZr0.9Y0.1O3-δ (BZY10, with Y substituting for 10 mol% Zr in BaZrO3)-supported Ru catalyst (Ru/BZY10) exhibited a high NH3 synthesis rate (4.00 mmol h−1 g-cat.−1) under the following reaction conditions: S.V. = 36 L h−1 g-cat.−1, T = 400 °C, P = 0.1 MPa. Furthermore, the calcination at 1200 °C of BZY10 enhanced the catalytic performance of Ru/BZY10 (4.63 mmol h−1 g-cat.−1 at 400 °C). Considering the NH3 synthesis rate per Ru amount, the optimal amount of Ru loading was 2.0 wt%. Furthermore, the addition of K and Cs to Ru/BZY10 can further improve the catalyst performance, which is found to be comparable to that of the other reported catalysts and is due to the electron-donating effect to active sites of Ru species. Based on various characterizations, we conclude that the particle size of Ru, the presence of BaCO3 and BaO crystalline phases, and the coverage of Ba species strongly affect the catalyst performance. Display omitted •Y-doped BaZrO3 and BaCeO3-supported Ru catalysts were evaluated for NH3 synthesis reaction.•Ru/BaZr0.9Y0.1O3-δ catalyst exhibited the highest performance for NH3 synthesis at 0.1 MPa.•Optimal conditions of BaZr0.9Y0.1O3-δ calcination temperature and Ru loading were 1200 °C and 2.0 wt%.•The addition of K and Cs to Ru/BaZr0.9Y0.1O3-δ promoted the performance due to electron donation to Ru.