Photocatalytic reduction of CO 2 has attracted enormous interest as a sustainable and renewable source of energy. In the past decade, numerous bulk-type semiconductors have been developed, but the existing designs suffer many limitations, namely rapid recombination of charge carriers and weak light absorption ability. Herein, a bottom-up approach was developed to design atomically thin sulfur-doped Bi 2 WO 6 perovskite nanosheets (S-BWO) with improved reduction ability, extended visible light absorption, prolonged lifetime of charge carriers, enhanced adsorption of CO 2 , and reduced work function. Compared with pristine Bi 2 WO 6 (P-BWO), S-BWO nanosheets exhibited a 3-fold improvement in photocatalytic reduction of CO 2 under simulated sunlight irradiation. Experimental studies and density functional theory calculations revealed the synergistic roles of atomically thin nanosheets and S atoms in promoting photocatalytic efficiency., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)