The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence ofvarious percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnOnanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by differenttechniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV–visible absorption spectroscopy. Further, the mostphotocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygendemand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail.