We demonstrated the fabrication of ZnO nanorods and nanowalls directly on flexible substrates by combining a hydrothermal growth technique with nanoporous templates obtained from block copolymers. First, templates with cylindrical nanopores in two sizes and a template with nanogrooves were fabricated on flexible substrates by employing block copolymers with different molecular weights. From these nanotemplates, we synthesized vertically oriented ZnO nanorods with controlled diameters and ZnO nanostructures in a wall shape. Because the ZnO nanostructures were produced without an electrically insulating epitaxial layer, the semiconducting nature of the ZnO nanorods was characterized as synthesized. Thus, this combined method of hydrothermal growth and block copolymer templates for ZnO nanostructures can be directly applied to flexible electronic devices without alteration of the substrate.