Microbial CO2 electroreduction (mCO2ER) offers a promising approach for producing high‐value multicarbon reductants from CO2 by combining CO2 fixing microorganisms with conducting materials (i. e., cathodes). However, the solubility and availability of CO2 in an aqueous electrolyte pose significant limitations in this system. This study demonstrates the efficient production of long‐chain multicarbon reductants, specifically carotenoids (~C40), within a wet amine‐based catholyte medium during mCO2ER. Optimizing the concentration of the biocompatible CO2 absorbent, monoethanolamine (MEA), led to enhanced CO2 fixation in the electroautotroph bacteria. Molecular biological analyses revealed that MEA in the catholyte medium redirected the carbon flux towards carotenoid biosynthesis during mCO2ER. The faradaic efficiency of mCO2ER with MEA for carotenoid production was 4.5‐fold higher than that of the control condition. These results suggest the mass transport bottleneck in bioelectrochemical systems could be effectively addressed by MEA‐assissted mCO2ER, enabling highly efficient production of valuable products from CO2. mCO2ER offers a promising approach for the production of high‐value multicarbon reductants from CO2 by combining CO2 fixing microorganism with cathode. We demonstrate the efficient production of multicarbon reductants, within a wet amine‐based catholyte medium during mCO2ER. A catholyte medium containing biocompatible CO2 absorbent redirected the carbon flux towards carotenoid(~C40) production from CO2 and electricity.