Isolated cobalt atoms have been successfully decorated onto the surface of W18O49 ultrathin nanowires. The Co-atom-decorated W18O49 nanowires (W18O49@Co) greatly accelerate the charge carrier separation and electron transport in the catalytic system. Moreover, the surface decoration with Co atoms modifies the energy configuration of the W18O49@Co hybrid and thus boosts the redox capability of photoexcited electrons for CO2 reduction. The decorated Co atoms work as the real active sites and, perhaps more importantly, perform as a reaction switch to enable the reaction to proceed. The optimized catalyst delivers considerable activity for photocatalytic CO2 reduction, yielding an impressive CO generation rate of 21.18 mmol g-1 h-1.