As visible light photocatalysts, narrow bandgap semiconductors can effectively convert solar energy to chemical energy, exhibiting potential applications in alleviating energy shortage and environmental pollution. Cu₂O hollow spheres with a narrow band gap and uniform hierarchical structures have been fabricated in a controlled way. The one-pot solvothermal method without any template is simple and facile. The morphologies, crystal structures, composition, specific surface areas, and optical and photoelectric properties of the products were analyzed by various techniques. The hollow and solid Cu₂O spheres could be fabricated by controlling the reaction time, and a possible growth process of the Cu₂O hollow spheres was revealed. The degradation of methyl orange (MO) was used to investigate the visible-light catalytic properties of the Cu₂O samples. More than 90% of MO is degraded under visible light illumination of 20 min, exhibiting a quick catalytic reaction. The rate constant of the Cu₂O hollow spheres was 2.54 times and 46.6 times larger than those of the Cu₂O solid spheres and commercial Cu₂O powder, respectively. The possible photocatalytic mechanism of MO was revealed over Cu₂O hollow spheres through the detection of active species. The as-prepared Cu₂O hollow spheres display improved visible-light catalytic activity and stability, indicating their potential application in wastewater treatment.