Photoactive and non-hazardous kaolinite/ZnO nanocomposite with 50 wt.% of ZnO nanoparticles was prepared using simple and cheap hydrothermal method. The resulting solid phase was separated by decantation, and dried at 105 °C. Calcination of the nanocomposites at 600 °C led to the kaolinite-metakaolinite phase transformation, to further growth of ZnO crystallites, and to significant increase in photodegradation activity. Whereas, for the several applications, e.g., in brake industry, the larger amount of composites is needed, thus, the evaluation of the reproducibility of preparation process is one of the crucial parameter. Prepared nanocomposites were deeply characterized by using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Rietveld quantitative phase analysis. Photodegradation activity was evaluated by the discoloration of Acid Orange 7 aqueous solution under UV irradiation. All used analytical techniques and methods confirm the reproducibility of the preparation process and as well that ZnO nanoparticles are anchored tightly on the clay surface which prevents the release to the environment.