Hierarchical ZnO nanostructures were synthesized via a low temperature hydrothermal method. The hierarchical ZnO nanostructures consisted of many porous ZnO nanowires that were grown in six symmetrical directions forming disk-like shapes. A dye-sensitized solar cell (DSSC) based on the ZnO hierarchical nanostructures was made, and showed improved performance than a DSSC based on ZnO nanowires arrays. The results suggest that the hierarchical ZnO nanostructures are promising for application in DSSC.