The photocatalytic reduction of CO₂ is a promising strategy to generate chemical fuels. However, this reaction usually suffers from low photoactivity because of insufficient light absorption and rapid charge recombination. Defect engineering has become an effective approach to improve the photocatalytic activity. Herein, ultra-thin (~ 4.1 nm) carbon-doped Bi₂WO₆ nanosheets were prepared via hydrothermal treatment followed by calcination. The ultra-thin nanosheet structure of the catalyst not only provides more active sites but also shortens the diffusion distance of charge carriers, thereby suppressing charge recombination. Moreover, carbon doping could successfully extend the light absorption range of the catalyst and remarkably promote charge separation, thus inhibiting recombination. As a result, the as-prepared Bi₂WO₆ photocatalyst with ultra-thin nanosheet structure and carbon doping exhibits enhanced photocatalytic CO₂ reduction performance, which is twice that of pristine ultra-thin Bi₂WO₆ nanosheet. This study highlights the importance of defect engineering in photocatalytic energy conversion and provides new insights for fabricating efficient photocatalysts.