In recent years, surface modification methods have gained significant attention in scientific research and advanced industries as an effective approach for improving component performance and efficiency. One of the novel technologies in this field is the Ultrasonic Peening (UP) process, which enhances the physical, mechanical, and even chemical properties of materials by applying repeated, high-frequency impacts to the component surface.This study investigated the effect of ultrasonic peening on the wear behavior of A356 aluminum alloy at various temperatures. Pin-on-disk tests were conducted over a temperature range from ambient to 300°C. The results indicated that, contrary to initial expectations, the ultrasonic peening treatment led to an increase in the wear rate across all temperatures. At room temperature, the wear rate of the peened samples was approximately 90% higher than that of the unpeened samples. This trend continued at elevated temperatures, with the wear rate showing an increase of about 62% at 300°C. Furthermore, the coefficient of friction was consistently higher for the peened samples under all test conditions. The increase in wear can be attributed to surface heterogeneity, stress concentration, and high dislocation density; however, definitive confirmation of this mechanism requires crystallographic analyses. In conclusion, the findings highlight the necessity of optimizing ultrasonic peening parameters to achieve a genuine improvement in the high-temperature wear resistance of A356 aluminum alloy.