Photocatalytic CO2 reduction holds great promise to solve energy shortage and global warming. Nb2O5 has demonstrated superiority in CO2 activation and selectivity regulation, but suffers from poor light absorption ability and fast carrier recombination. To tackle these problems, we designed and synthesized ultrathin Nb2O5 nanosheets which were decorated with tiny NiP nanoparticles as cocatalyst. In this way, light absorption range broadened, carrier migration distance reduced, charge transfer resistance decreased, and surface reaction kinetics promoted. Consequently, the as‐prepared NiP/Nb2O5 showed notably enhanced activity (148.7 µmol·g‐1) and selectivity (82.1%) towards CO, as well as remarkable stability. This work paves the way for cheap and earth abundant alternatives as cocatalysts and deepens the understanding of their functions in the activity and selectivity of CO2 photoreduction.