Mesoporous Ta 2 O 5 was synthesized by a surfactant-assisted sol–gel method under mild condition. Based on XRD pattern, the products, obtained by calcination at 600 and 700°C, were found to be in the amorphous and the orthorhombic phases, respectively. The morphology and pore structure of the products were characterized by SEM, TEM and nitrogen adsorption–desorption measurements. The photocatalytic activity was evaluated by measuring the degradation of methylene blue under UV irradiation. Mesoporous orthorhombic Ta 2 O 5 showed higher photocatalytic activity than that of the mesoporous sample in the amorphous state, although orthorhombic Ta 2 O 5 had a lower surface area. The reason of this enhanced photocatalytic property is discussed.