Incomplete NH3 decomposition is a major challenge in direct-NH3 solid oxide fuel cells (DA-SOFCs) which limits cell performance. Herein, we propose to employ thermally stable NH3 decomposition catalysts in DA-SOFCs during NH3 fueling. The Ba/Ni/Al2O3 catalyst synthesized from a layered double hydroxide via rapid hybrid microwave annealing shows high Ni dispersion and suppresses particle migration. The Ba/Ni/Al2O3 achieved 82 % NH3 conversion at 550 °C with an H2 production rate of 26.8 mmol gcat−1 min−1. Furthermore, the catalyst-integrated DA-SOFC achieved a peak power density of 0.56 W cm−2 at 650 °C under NH3, comparable to that under H2–N2 conditions (0.61 W cm−2). In contrast, a commercial DA-SOFC fed with NH3 exhibited a significantly lower peak power density of 0.43 W cm−2. These results demonstrate that integrating an active catalyst with DA-SOFCs enables efficient on-site H2 generation and utilization in NH3-fueled power systems.