We report here on the multiproton-multielectron electrochemical reduction of CO 2 in homogeneous solution by using (TOA) 6 [α-SiW 11 O 39 Co(_)] (TOA = tetraoctyl ammonium; _ = vacant position in the coordination sphere of Co) as an electrocatalyst. First, the electrochemical behavior of (TOA) 6 -[α-SiW 11 O 39 Co(_)] was analyzed in detail by cyclic voltammetry in dichloromethane, studying the influence of the pres- [a]3642 ence of protons and/or CO 2 . These preliminary results were further used to optimize the conditions of electrolysis in terms of reduction potentials. Analysis of the electrolysis products in the gas and liquid phases show the formation of CO and HCHO without formation of H 2 . Our results tend to show that the (TOA) 6 [α-SiW 11 O 39 Co(_)] polyoxometalate is a catalyst for CO 2 electroreduction, with unique selectivity.