Fe, N and C tri-doped polymorphic TiO2 nano-materials show good photocatalytic activity for Cr(VI) reduction under visible light irradiation. Display omitted •Fe, N and C atoms were successfully tri-doped into the nanostructures of Fe-N-C-TiO2.•The band gap energy of Fe-N-C-TiO2 reduced after (Fe, N and C) tri-doping.•Fe, N and C tri-doping in polymorphic TiO2 were effective for the photocatalytic reduction of Cr(VI). The (Fe, N and C) tri-coped polymorphic TiO2 (Fe-N-C-TiO2), containing anatase, rutile and brookite phase, were synthesized by a hydrothermal method. The tri-coped polymorphic TiO2 were characterized in detail by several techniques in terms of their structure, composition, optics, morphology, surface area, and so on. The photocatalytic activities of Fe-N-C-TiO2 nano-materials were examined under visible light illumination using Cr(VI) as target pollutant. The results showed that Fe/Ti weight ratio crucially determines the photocatalytic activity of Fe-N-C-TiO2 nano-materials. Fe-N-C-TiO2 nano-materials with Fe/Ti weight ratio of 0.30% exhibits highest photocatalytic activity than that of the other nano-materials under visible light irradiation, which can be attributed to the synergic effect of the higher BET surface area, separation rate of electron-hole pairs, more number of surface absorbed hydroxyl groups (OH), stronger absorption in the visible-light region and optimum Fe/Ti weight ratio.