Simultaneous photocatalytic reduction of chromium(VI) to the less toxic Cr(III) and degradation of di-n-butyl phthalate (DBP) in aqueous TiO2 suspension under ultraviolet light irradiation was investigated. The batch experiments were carried out in a photoreactor equipped with 350 nm lamps. The system containing Cr(VI) and DBP showed the synergistic photocatalytic decontamination as DBP facilitated Cr(VI) reduction, whereas Cr(VI) accelerated DBP degradation. This study demonstrated for the first time that two important environmental pollutants Cr(VI) and DBP could be eliminated simultaneously using UV/TiO2 process. The intermediate products of DBP degradation were identified by gas chromatography-mass spectrometry, and the reaction mechanism was proposed.