Angle-resolved X-ray photoelectron spectroscopy (ARXPS) experiments were performed to study in situ the reaction at the film–substrate interface during metal organic chemical vapor deposition (MOCVD) growth of TiO2 thin films deposited on the silicon substrate. The in-depth distribution of chemical species was determined using several ARXPS thickness calculation models considering either single or bilayer systems. By the comparison of two single-layermodels, the presence of a second layer composed of silicon oxidewas evidenced. High-resolution transmission electron microscopy (HRTEM) observations confirmed the stratification of the film in two layers, as well as the perfect wetting of the surface by TiO2, irrespective of the model used. The contribution of the ARXPS bilayer model was demonstrated by the agreement of the values of film thickness obtained by both techniques. Nevertheless, the correlation between each layer's thickness was only possible by taking into account chemical species mixing. Indeed, the presence of oxidised silicon in the upper TiO2 layer, in addition to that of the SiOx interlayer, has to be considered to interpret ARXPS results in a correct way.