The catalytic performance of Ru-NAD-type complexes [Ru(tpy)(pbn)(CO)(2+) ([1](2+); tpy = 2,2';6',2 ''-terpyridine; pbn = 2-(pyridin-2-yl)benzo[b][1,5]naphthyridine) and the Ru-CO-bridged metallacycle [2](+) was investigated in the context of the electrochemical reduction of CO2 in H2O/CH3CN at room temperature. A controlled-potential electrolysis of [1](2+) and [2](+) afforded formate (HCOO-) as the main product, under concomitant formation of minor amounts of CO and H-2. Metallacycle [2](+) showed a higher selectivity toward the formation of HCOO- than [1](2+) (HCOO-/CO for [1](2+), 2.7; HCOO-/CO for [2](+), 7). The generation of HCOO- via a catalytic hydride transfer from the NADH-type ligands of [1](2+) and [2](+) to CO2 was supported by the experimental results and a comparison with the reduction of CO2 catalyzed by [Ru(tpy)(bpy)(CO)](2+) under similar conditions. A mechanism for the catalytic reduction of CO2 by [1](2+) and [2](+) was proposed based on the experimental evidence. The thus-obtained results may help to expand the field of NADH-assisted reduction reactions.