A four-electron-reduced ruthenium(II) NADH-type complex, [Ru(bbnpH₄)(CO)₂Cl](PF₆) (bbnpH₄ = 2,2′-(4-(tert-butyl)pyridine-2,6-diyl)bis(5,10-dihydrobenzo[b][1,5]naphthyridine)), has been successfully synthesized by mixing an NAD⁺-type ligand, bbnp (bbnp = 2,2′-(4-(tert-butyl)pyridine-2,6-diyl)bis(benzo[b][1,5]naphthyridine)), and [Ru(CO)₂Cl₂] under moderate water-gas-shift reaction conditions, which has been fully characterized by single-crystal X-ray structure analysis, ESI-TOF mass spectrometry, and NMR spectroscopy.