Ammonia is an important chemical for synthesized fertilizers traditionally and for a potential energy vector increasingly. Industrial ammonia synthesis through the Haber–Bosch process is energy-intensive and requires advanced materials to catalyze ammonia synthesis under mild conditions, whereas the utilization of ammonia as a hydrogen carrier via ammonia decomposition is facing a similar situation as well. The developed second-generation Ru-based catalysts performs superior activities over commercial Fe- or Ni-based catalysts; however, it remains challenging to construct effective Ru catalysts to achieve the usage of Ru metal affordably as well as further understanding the nature of Ru catalysis. This Perspective summarizes the recent contributions in engineering Ru-based catalysts via various strategies and related catalysis in ammonia synthesis and decomposition, and it discusses the similarities and differences of Ru catalysis in these reactions. Finally, an overview of this area and opportunities for further investigation are also provided.