Atomically precise (CdSe)₁₃ clusters, the smallest CdSe semiconductors, represent a unique class of materials at the boundary between nanocrystals and molecules. Despite their promising potential, low structural stability limits their applications as photocatalysts. Herein, we report photocatalytic hydrogen production using atomically precise (CdSe)₁₃ clusters. To improve stability in aqueous environments, we induce self-assembly into suprastructures, making them suitable for water splitting. Our findings demonstrate that Co²⁺ doping enhances the electrical properties of these clusters, while bipyridine serves as cocatalyst by interacting with Co²⁺ dopants and providing catalytic active sites. Through the synergistic effects of Co²⁺ doping and bipyridine, Co²⁺-doped (CdSe)₁₃ suprastructures achieve promising hydrogen evolution activity, surpassing those of undoped suprastructures or nanoclusters. Theoretical calculations confirm that Co²⁺ doping and bipyridine incorporation lower the hydrogen adsorption energy, consistent with the experimental results. These results highlight the potential of semiconductor (CdSe)₁₃ clusters as photocatalysts for sustainable hydrogen production.