Herein, a novel Ag2O/ZnWO4 Z-scheme heterojunction sonocatalyst was fabricated and characterized. The sonocatalytic activities of the Ag2O/ZnWO4 composites were evaluated by the decomposition of meloxicam (MLX) as a model of pharmaceutical substances. The results showed that Ag2O/ZnWO4 composites had excellent sonocatalytic performances for the decomposition of MLX under ultrasonic irradiation (90.60 ± 0.49%) compared with that of pure ZnWO4 (53.33 ± 1.79%). The best sonocatalytic decomposition efficiency of MLX was achieved with the optimum operational parameters, such as 0.5 g/L Ag2O/ZnWO4 composites, 10.0 mg/L MLX solution, ultrasonic irradiation power of 200 W and ultrasonic irradiation time of 120 min. The enhancement of sonocatalytic performances was attributed to the increasing adsorption of MLX to Ag2O/ZnWO4 composites and the production of reactive species. The results of trapping experiments and the calculated band positions suggested that the formation of Z-scheme heterojunction of Ag2O/ZnWO4 and the generated reactive species including hydroxyl radicals and holes acted pivotal partsin the sonocatalytic decomposition of MLX using Ag2O/ZnWO4 composites as a sonocatalyst. In addition, Ag2O/ZnWO4 composites displayed good stability and reusability in the sonocatalytic decomposition process. It is expected that the results can provide valuable information for the further investigations of Ag2O/ZnWO4 composites as a potential sonocatalyst in the environmental remediation.