Natural photosynthesis is an effective route for the clean and sustainable conversion of CO₂ into high‐energy chemicals. Inspired by the natural process, a tandem photoelectrochemical (PEC) cell with an integrated enzyme‐cascade (TPIEC) system was designed, which transfers photogenerated electrons to a multienzyme cascade for the biocatalyzed reduction of CO₂ to methanol. A hematite photoanode and a bismuth ferrite photocathode were applied to fabricate the iron oxide based tandem PEC cell for visible‐light‐assisted regeneration of the nicotinamide cofactor (NADH). The cell utilized water as an electron donor and spontaneously regenerated NADH. To complete the TPIEC system, a superior three‐dehydrogenase cascade system was employed in the cathodic part of the PEC cell. Under applied bias, the TPIEC system achieved a high methanol conversion output of 220 μm h⁻¹, 1280 μmol g⁻¹ h⁻¹ using readily available solar energy and water.