Hexagonal Ba5Nb4O15 nanorods and microdisks were synthesized by a sol-gel process at temperatures of 700 degrees-900 degrees C. The samples were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and UV-visible absorption spectroscopy. The visible light absorption edges of the Ba5Nb4O15 nanorods and microdisks corresponded to the band gap energies of 3.63 and 3.70 eV, respectively. This shows that the nanorod and microdisk-type structures are promising candidates for application in the miniaturization of microwave components.