Three-dimensional (3D) urchin-like zinc oxide (ZnO)/titanium dioxide (TiO₂) composite micronanostructures were first successfully synthesised using a facile electrochemical deposition method by depositing TiO₂ into the surface of as-prepared 3D urchin-like ZnO, and polydienes dimethylammonium chloride as polycation solution. Photoelectric properties of the single 3D urchin-like ZnO and the composite micronanostructures as dye-sensitised solar cell (DSSC) anodes were investigated. During the deposition reaction, the TiO₂ was exactly densely anchored onto the surface of 3D urchin-like ZnO with uniform size, which were characterised by scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The effects of different molar ratios of TiO₂ and ZnO for the composite structure's morphology and photocatalytic activity were investigated systematically. The results indicated that the composite micronanostructures exhibited a larger adsorption range (−450 nm) and higher photoelectric conversion efficiency due to the synergistic effects, planar heterojunction, and mesoporous structure. When used as photoanodes for DSSCs, the I–V curve showed the photoelectric conversion efficiency of the novel composite was increased by 17.7% of that compared with the single 3D urchin-like ZnO. These features collectively demonstrated the composite has a considerable potential for various applications in photocatalysis materials.