In this research, Fe-doped TiO2 nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10wt%) were prepared by a sol-gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1eV. Photocatalytic results indicated that TiO2 had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO2 nanoparticles. Among the samples, Fe-1wt% doped TiO2 nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.