We report the first hematite-based photoelectrochemical (PEC) biosensor platform to detect NADH under visible-light irradiation. To enhance the electrical signal of photoanodes, we employed mussel-inspired polydopamine which immobilizes redox mediators on hematite. The enzymatic PEC biosensor enabled the detection of glucose, ethanol, and lactate, and even showed successful detection of glucose in human plasma, suggesting the practical usefulness of our platform.