Flower-like BiOBr hierarchical structures were successfully prepared via a surfactant-free hydrothermal method. The structure and properties of the as-prepared samples were characterized by X-ray diffraction, energy dispersion X-ray, field-emission scanning electron microscopy and UV-vis diffuse reflectance spectroscopy. Characterization results elucidated that the flower-like BiOBr were built from numerous well-developed nanosheets and formed an open porous structure through oriented aggregation. The as-prepared samples were also found to be well-crystalline and possessing tetragonal phase pure BiOBr. Interactive effects of catalyst loading, initial substrate concentration, solution pH and visible light exposure time were also investigated. Under optimized conditions, 69.7% degradation of sunset yellow was achieved with 1.31 g/L catalyst loading, 10 mg/L sunset yellow concentration, pH 3.0 and 180 min irradiation time. The photocatalytic technology using flower-like BiOBr hierarchical structures had the potential to effectively purify wastewater.