We have reported the formation of a thin manganese cobalt sulfide (MCS) film on a fluorine-doped SnO2 (FTO) substrate by a facile electrodeposition method for fabricating quantum-dot-sensitized solar cells (QDSSCs). The resulting FTO/MCS films are subsequently employed as counter electrodes (CEs) for cadmium selenide-based QDSSCs. The QDSSC with the FTO/MCS CE provided significantly enhanced short circuit current and fill factor, resulting in very high overall energy conversion efficiency (3.22%) compared to that with the Pt CE (1.08%) under 1-sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the binary transition metal sulfide in addition to the excellent electrical contact at the interface between the electrodeposited MCS film and the FTO. Furthermore, the FTO/MCS exhibit excellent electrochemical stability, unlike the conventional Pt CE. These findings suggest that FTO/MCS should be a promising electrocatalytic electrode material for practical energy conversion applications. (C) 2018 The Electrochemical Society.