Commercially pure titanium grades 1 (Ti), 2 (TiG2) and Ti-6Al-4V alloy grade 5 (TiG5) are used for many different types of biomaterials because of their excellent biocompatibility. Most of the biocompatibility of titanium is due to the formation of a passive thin oxide film (TiO2) in the presence of oxidant environments; it is basically found in two of its allotropic forms; rutile and anatase. The aim of this investigation was to evaluate the effect of thermal oxidation on effective thermal diffusivity measured by the open photoacoustic cell technique. Two sets of each material were prepared and submitted to heat treatment in air at 600 and 700 °C. The effective thermal diffusivity was correlated with the different oxide phases produced on the surfaces of the samples that were identified and quantified by Raman spectroscopy. It was observed that the predominant structure of TiO2, rutile or anatase, strongly influenced the effective thermal diffusivity of the samples.