We report on well-aligned TiO₂ nanorod arrays formed on a titanium substrate using acetone as the oxygen source in the oxidation of Ti at 850 °C. For comparison, TiO₂ films were also prepared by oxidizing Ti substrates with pure oxygen and with a mixture of argon with a low concentration of oxygen. X-Ray diffraction, transmitting electron microscopy and Raman studies show that all the TiO₂ films fabricated in this study have the same rutile phase. However, the microstructures of these TiO₂ films, characterized using scanning electron microscopy, are dramatically different. The use of pure oxygen yielded crystalline grain films, whereas the use of argon with a low concentration of oxygen produced random nanofibers growing from the ledges of the TiO₂ grains; in contrast, highly dense and well-aligned TiO₂ nanorod arrays were formed with acetone as the oxygen source. Measurements of the water contact angle on these samples show that the wetting properties of the TiO₂ films are dictated by their structure, varying from a hydrophilic surface (polycrystalline grains) to hydrophobic (random nanofibers), and towards a highly hydrophobic surface (well-aligned nanorod arrays). The origin of the different wetting properties and the possible growth mechanisms for these oxide films are discussed.