In this study, nickel oxide nanostructured particles were produced by hydrothermal method. X-Ray diffraction (XRD) and transmission electron microscope (TEM) measurements were performed to determine the physical properties of these nanostructured particles. When XRD results are examined, it is seen that NiO nanoparticles are cubic structure. It is understood from the TEM images that these particles are nanostructured. The photocatalytic activities of nanostructured particles were investigated. This examination was carried out by using methylene and methyl blue dyes under the xenon lamp. It has been observed that the photocatalytic degradation rates are high. It was found that the degradation of NiO nanostructured particles on methylene blue was about 59%, the decomposition on methylene blue added H2O2 was about 96% and the degradation on methyl blue was about 92%.