Novel hierarchical bow-like Cu₂O crystals were successfully synthesized via a facile room temperature solution reaction using PVP as a structure-directing agent in the presence of NaBH₄. The morphology evolution of the hierarchical bow-like Cu₂O crystals were observed to be tunable as a function of reaction parameters, such as the reaction time, the quality of PVP and the reaction temperature. The possible growth mechanism of hierarchical bow-like Cu₂O crystals was investigated. It involves the formation process of the intermediate octahedra Cu₂O crystals and subsequent oxidation–erosion process from octahedra to hierarchical bow-like Cu₂O crystals. It was found that the octahedra Cu₂O crystals are a necessary intermediate for the formation of the bow-like Cu₂O crystals. The prepared hierarchical bow-like Cu₂O crystals exhibited a higher photocatalytic activity for photodegradation of rhodamine B aqueous solution under visible light illumination than the other prepared Cu₂O crystal samples with different morphologies (nanoparticles and octahedra) because of its large surface area and specific hierarchical bow-like structure.