In this study, Al-doped ZnO nanoflowers were fabricated on conductive substrates via a simple electrodeposition process. The Al-doped ZnO nanoflowers are three-dimensional micro/nano hierarchical structures composed of numerous nanosheets. The chemical composition and crystal structure of the as-synthesized nanoflowers were characterized by EDS, XPS, XRD and HRTEM. It was found that the Al doping led to the decrease of the band gap of ZnO from 3.21 eV to 3.07 eV. Considering the large surface areas, the Al-doped ZnO nanoflowers were used as the photocatalyst for degradation of methyl orange, and exhibited a significantly enhanced performance comparing with the undoped ZnO nanostructures. The good photocatalytic performance should be related to the large surface areas of the nanoflowers and the more free carriers in the Al-doped ZnO, which are introduced by the dopants.