A joint experimental and theoretical study is carried out to investigate the structural and absorption properties of the C212 organic dye adsorbed onto the TiO2 anatase surface. UV–Vis measurements evidence a significant blue shift of the main absorption band of the dye upon absorption, which is well reproduced by theoretical calculations combining tight-binding and time-dependent DFT calculations. The blue shift is substantiated by a loss in the efficiency of the light-induced charge transfer along the anchored dye, which partly originates from the deprotonation of the carboxylic acid function.