Hierarchical ZnO hexagonal nanorods were successfully synthesized on fluorine-doped tin oxide (FTO) glass substrates via a simple electrodeposition from DMSO-H 2 O solution. The formation process was studied in detail by observing time-dependent products, and an oriented attachment mechanism is suggested for the growth of these hierarchical hexagonal nanorods. The influence of reaction temperature and solvent on the morphologies of products was also investigated. Interestingly, the optical band gap of hierarchical ZnO nanorods can be tuned by simply changing the reaction temperature during the electrodeposition process.