Co₃Mo₃N has been reported to have activity for the synthesis of ammonia surpassing that of industrial Fe catalysts under certain conditions. However, so far the research has largely focused on unsupported Co₃Mo₃N. We report a comprehensive study on the catalytic activity of Co₃Mo₃N when supported on two distinct MgO substrates. Our findings reveal that the method of MgO preparation plays a crucial role in influencing surface basicity. Remarkably, Co₃Mo₃N supported on single-crystalline MgO demonstrates significantly enhanced catalytic activity, achieving a 162.0 mmol g⁻¹metal h⁻¹ rate. This surpasses the performance on commercial MgO support (41.2 mmol g−1metal h−1) and unsupported Co₃Mo₃N (15.0 mmol g−1metal h−1). While kinetic analyses show no substantial differences between the two supported catalysts, spectroscopic studies employing CO₂ and N₂ temperature-programmed desorption (TPD) reveal a richer array of basic sites and adsorption/desorption phenomena on the single-crystalline MgO support. These catalysts exhibit exceptional stability. The drastically reduced Co/Mo loading amounts in comparison to the bulk form, make the commercialization of Co₃Mo₃N catalysts more practical.