A series of nickel(II) complexes bearing tetradentate macrocyclic N4, N3S, and N3P ligands were synthesized, and their photocatalytic activity toward proton reduction has been investigated by using [Ir(dF(CF3)ppy)2(dmbpy)]PF6 (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine and dmbpy = 4,4′-dimethyl-2,2′-dipyridyl) as the photosensitizer and triethylamine (TEA) as the sacrificial reductant. The complex [Ni(L4)]2+ (L4 = 2,12-dimethyl-7-phenyl-3,11,17-triaza-7-phospha-bicyclo[11,3,1]heptadeca-1(17),13,15-triene), which bears a phosphorus donor atom, shows the highest efficiency with TON up to 5000 under optimized conditions, while the tetraaza macrocyclic nickel complexes [Ni(L1)]2+ and [Ni(L2)]2+ (L1 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),2,11,13,15-pentaene; L2 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),13,15-triene) show lower photocatalytic activities. Transient UV–vis absorption and spectroelectrochemical experiments show that Ni(II) is re...