Solvent modification with a mixture of tetrahydrofuran and water in a proportional volume ratio of 50% has been employed to enable poly(methylmethacrylate)-b-polyethylene oxide diblock copolymer to be used as a template for preparing nanohybrid thin films containing highly ordered arrays of titanium dioxide (TiO2) nanoparticles. With control of the processing parameters involved in the block copolymer templating, nanoarrays consisting of nanocrystalline TiO2 particles were successfully assembled in the hexagonal-like or cubical-like hierarchical structures, as revealed by TEM studies. The phases and chemical nature of the titania nanoparticles have been confirmed by Raman and XPS spectroscopies. A significant enhancement in nanocrystallinity of the TiO2 phase in the nanohybrid thin films was achieved by the application of an appropriate hydrothermal treatment in high-pressure water vapor at 150°C. The nanocrystallinity strongly affects the UV absorbance and photoluminescence emission of the nanohybrid thin films.