This work explores the potential of thin films composed of shape-controlled colloidal TiO2 nanocrystals in optical gas sensing applications. To this purpose, an optical characterization of nanocrystal thin films has been performed by means of UV–vis spectroscopy and surface plasmon resonance (SPR) technique. In particular, this technique has been used as optical transduction method to test the sensing properties of the oxide films towards alcohol vapours. Numerical fitting routines have been employed to evaluate quantitatively the changes in the characteristic optical parameters for the investigated films during the sensing process. It has been found that rod-shaped TiO2 nanocrystals provided with close-packed monolayers of long-chain surfactants on their surfaces, maximize the sensor response, as they may help to achieve a higher degree of alcohol accumulation on the active material.