Alkaline earth oxide (MgO, CaO, SrO) doped TiO2 catalysts prepared by impregnation method were successfully used in the photocatalytic degradation of 4-chlorophenol (4-CP) under UV irradiation. The materials were characterized by XRD, BET, FT-IR, DRS, PL, SEM and TEM techniques. Alkaline earth metal oxides resulted in an enhanced efficiency of the TiO2 photocatalyst. The 10 wt% MgO TiO2 showed the highest percentage of 4-CP degradation (100%) and highest reaction rate (0.82 mg L-1 mm(-1)) in 1 h. It was also found that the catalytic activity of 10MgO-TiO2 was found to be higher than nano TiO2 and P-25 photocatalyst. The photocatalytic performances are in the orders of: 10MgO/TiO2 > 10CaO/TiO2 > 10SrO/TiO2. Alkaline earth oxide effectively decreases the band gap of the TiO2. The enhanced adsorption of 4-CP over the catalyst surface and decrease in particle size as a result of Mg2+ loading is suggested to be the cause for higher activity of the catalyst. The profound effect of alkaline earth oxide doped TiO2 for 4-chlorophenol is generally considered due to the entry of Mg2+ into the lattice of nano TiO2 and high dispersion. (C) 2012 Elsevier B.V. All rights reserved.