In this study, we promoted CeO2 into ZrO2 nanoparticles, using ultrasonic assisted-method, as an effort to improve the sonocatalytic performance of ZrO2 nanoparticles. The molar ratios of CeO2to ZrO2 were controlled as follows 0.1:1, 0.3:1, 0.5:1, and 1:1. The prepared samples were characterized by various measurements, such as X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). XRD measurements showed tetragonal and cubic phases for ZrO2 and CeO2, respectively. TGA showed that mass degradation below 150°C was attributed to the loss of bound water from the surface of ZrO2. The sonocatalytic activity of the prepared samples was examined by sonodegradation of methylene blue (MB) under ultrasound irradiation. The results showed that the presence of a certain amount of CeO2 in ZrO2 nanoparticles improved its efficiency in degrading MB. The maximum degradation of MB was achieved at a molar ratio of 0.3:1. The catalyst dosages were also varied from 0.1 to 0.4 g/L, and the optimum catalyst dosage was found to be 0.3 g/L. From several reactive species, namely holes, electrons, and hydroxyl radical, holes were found to be the main reactive species with a significant role in degrading MB. In addition, the reusability test verified that the prepared samples were reusable.