Sr2Ta2O7 nanosheets have been synthesized by a hydrothermal method without using any template. The thickness, widths, and lengths of Sr2Ta2O7 nanosheets are about 10-50 nm, 50-150 nm, and 500 nm, respectively. The optimum conditions for the formation of the nanosheets are maintaining the reactants at 260 degrees C for 7 days. on basis of the experimental data, a possible formation mechanism of the nanosheets under the hydrothermal conditions was proposed. The photocatalytic activity for water splitting was investigated under ultraviolet irradiation. It has been found that Sr2Ta2O7 nanosheets, compared to the bulk Sr2Ta2O7 sample, showed a higher photocatalytic activity even in the absence of a cocatalyst. The higher activity of the hydrothermally synthesized sample is attributed to its larger surface areas and nanoscale structure. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.