Photoelectrochemical (PEC) water splitting provides a promising strategy for H production. However, its performance is limited by severe carrier recombination and sluggish water oxidation kinetics. While numerous strategies, namely, elemental doping, morphology engineering, heterojunction formation, and catalyst modification, have been extensively explored to enhance the PEC performance, the application of external magnetic fields (MFs) to affect the catalysis or charge carrier dynamics remains yet to be exploited. Herein, BiVO is first selected as a representative photoanode, demonstrating that an ultrathin ferromagnetic coating based on FeTiO, when combined with an external MF, boosts its solar water oxidation performance. The combined analyses of the charge transfer and separation efficiency together with ultraviolet photoelectron spectroscopy and transient absorption spectroscopy data revealed that the MF positively affects the band alignment across the BiVO/FeTiO interface, improving the charge separation, while the oxygen evolution at the FeTiO/electrolyte interface was promoted. Finally, we expand this concept to other metal oxide photoanodes, such as TiO, WO, and FeO, demonstrating the universality of such an approach. Overall, this work pioneers a novel route to harvest external MFs and improve the PEC response of common nonmagnetic semiconductor photoelectrodes in photoelectrocatalytic conversion.