During Ti:LiNbO3integrated optical waveguide fabrication the (Ti0.65Nb0.35)O2forms at temperatures ranging from 700 to 950 °C, after the Ti oxidation which occurs owing to Ti reaction with oxygen atoms of the surrounding atmosphere and/or of LiNbO3substrates. The (Ti0.65Nb0.35)O2compound has been characterized using scanning electron microscopy, secondary ion mass spectrometry, Auger electron spectroscopy, Rutherford backscattering in channeling conditions, and x‐ray diffraction. Results show that the (Ti0.65Nb0.35)O2phase grows epitaxially on bothZ‐ andY‐cut substrates, the quality depending on both annealing atmosphere and film thickness. The film behaves as a real source for Ti diffusion and consequently is consumed at increasing annealing temperatures and/or times. We did not observe Li‐Ti‐O compounds, although a small amount of Li was detected in the surface layer.