In the present work, ultrasonic-assisted and co-precipitation methods were adopted to synthesize Ag/Fe3O4/ZrO2/Nanographene Platelet (NGP) composites. The as-prepared composites were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and thermal gravimetric analysis (TGA). The photo- and sonophotocatalytic activities of the composites were evaluated by removing methylene blue (MB) in an aqueous solution under UV and a combination of ultraviolet (UV) and ultrasound irradiation, respectively. According to the experimental results, the incorporation of NGP in the Ag/Fe3O4/ZrO2 composites could improve the catalytic performance of MB degradation in both the photo- and sonophotocatalytic activities. The sonophotocatalytic process using UV and ultrasound irradiation exhibited better catalytic performance compared to that using UV light irradiation alone. Besides, the effect of the photocatalyst dosages, the initial concentration of MB, scavengers of reactive species, and the reusability was investigated in detail.