Herein, we established an iridium- and molybdenum-catalysed process for the synthesis of ammonia from dinitrogen that takes place under ambient reaction conditions and under visible light irradiation. In this reaction system, cationic iridium complexes bearing 2-(2-pyridyl)phenyl and 2,2’-bipyridine-type ligands and molybdenum triiodide complexes bearing N-heterocyclic carbene-based PCP-type pincer ligands acted as cooperative catalysts to activate 9,10-dihydroacridine and dinitrogen, respectively. Interestingly, under visible light irradiation, 9,10-dihydroacridine acted as a one-electron and one-proton source. The findings of this study provide a novel approach to catalytic nitrogen fixation that is driven by visible light energy. The reaction of dinitrogen with 9,10-dihydroacridine was not thermodynamically favoured, and it only took place under visible light irradiation. Therefore, the described reaction system is one that affords visible light energy–driven ammonia formation from dinitrogen. The findings reported herein can contribute to the development of novel next-generation nitrogen fixation systems powered by renewable energy.