TiO₂ (rutile) thin films were deposited via a hydrothermal process by adjusting the amount of ethanol, deposition time, and temperature. Especially, various amounts of ethanol generated different degrees of supersaturation in precursor solution. It allowed us to systematically change the width, lengths, and crystallinity of a vertically aligned 1‐D nanorod structure of TiO₂ films. The oriented attachment, confirmed by scanning electron microscopy and transmission electron microscopy, was shown to be responsible for their lateral growth of TiO₂ nanorods bundled by numerous well‐oriented nanowires and their vertical growth. TiO₂ nanorod thin films were also characterized via X‐ray diffraction and UV‐Vis‐NIR spectrophotometer to find a correlation between the process conditions and nanostructural evolution. Dye sensitized solar cells were assembled to relate the nanostructures of TiO₂ films with the effectiveness of its role as a photoelectrode.