Decolorization of the azo dye Basic Blue 41 was studied separately by photocatalysis in the presence of nanocrystalline Titania films or oxidation by Photo Fenton. Optimization procedures helped to determine the optimal quantity of TiO2 photocatalyst, hydrogen peroxide and Fe+2 stop ions. By simultaneous treatment of an aqueous solution of the dye with TiO2 and Photo Fenton, a synergy effect demonstrated itself giving an extensive acceleration of the decolorization of the dye and a large increase of the apparent first-order rate constant. This synergy is most probably related with the interaction of H2O2 with Titania and the interference of iron ions in this interaction.