In the present study a flower like ZnO nanostructure has been synthesized by using simple hydrothermal route without any catalysts, templates or substrates. The phase structure and morphology of the synthesized ZnO has been characterized by XRD, SEM and TEM. The room temperature photoluminescence (PL), diffuse reflectance spectra (DRS), FT-IR spectra and BET surface area have also been examined. Furthermore the application of the prepared ZnO as a photocatalyst was investigated for the decolorization of pararosaniline chloride dye and its simulated dyebath effluent. Finally the comparison of photocatalytic activity of commercial and synthesized ZnO has been made. Experiments were also performed to investigate the reusability and stability of the synthesized ZnO. (C) 2011 Elsevier B.V. All rights reserved.