As an important environmental factor, temperature affects the growth, reproduction, physiology, behavior, and offspring phenotype of reptiles. The influence of thermal acclimation on physiological and behavioral performance has been documented in many ectotherm animals, although the acclimation responses of different species may be not identical. The red-eared slider turtle (Trachemys scripta elegans) is an alien invasive species found in China. Wild populations have been found to be a threat to local biodiversity in many areas. In this paper, critical thermal minima (CTMin) and critical thermal maxima (CTMax) are used to assess the thermal resistance of juvenile red-eared slider turtles. In addition, the selected body temperature (Tsel) is used to determine the species' preferred temperature. Our study aimed to determine whether acclimation temperature would affect the Tsel, CTMin, CTMax, thermal resistance range (TRR), the activity of superoxide dismutase (SOD) and catalase (CAT), and the malondialdehyde (MDA) content of the skeletal muscles, cardiac muscles, and liver. In order to examine their thermal adaptive performance at different temperatures, we selected 90 juvenile turtles weighing between 40.0 and 44.3 g, randomly divided them into 5 groups with similar average weights (P=0.141), and acclimated them to five thermal conditions (16, 20, 26, 32℃ and 36℃) for 30 days. After acclimation, Tsel were measured using a thermometer (UT-325) in thermal gradient groove, while CTMin and CTMax were measured in binder incubators. SOD and CAT activity, as well as the MDA content were measured using commercial kits produced by Jiancheng Biotech Co. Ltd., Nanjing, China, according to the manufacturer's instructions. Then, a one-way ANOVA was used to test the effects of acclimation temperature on Tsel, CTMin, CTMax, TRR, SOD and CAT activity, and the MDA content of different tissues. The results showed that acclimation temperature had significant effects on the Tsel (P < 0.0001), CTMin (P < 0.0001), and CTMax (P < 0.01) of juvenile turtles, but had no significant effect on the TRR (P=0.212). Tsel, CTMin, and CTMax increased with acclimation temperature. Acclimation temperature had a significant impact on SOD activity in the skeletal muscles, cardiac muscles, and liver, as well as on the MDA content of the liver (all P < 0.05). However, it had no effect on the MDA content of the skeletal and cardiac muscles (all P > 0.05). There was higher SOD activity in the skeletal and cardiac muscles at high temperatures (26-36℃) than at low temperatures (16-20℃); meanwhile, in the liver, higher SOD activity and MDA content were observed at medium temperatures (20-32℃). Acclimation temperature had a significant effect on CAT activity in the cardiac muscles and liver (all P < 0.05), but no effect on that in skeletal muscles (P=0.55). In cardiac muscles, CAT activity was significantly lower at 36℃ than at other temperatures, while in the liver CAT activity peaked at 16℃. This indicates that acclimation temperature affects the selected body temperature and thermal tolerance of juvenile red-eared slider turtles, with higher temperatures generally having more favorable effects. The antioxidant activity in the tissues was also affected by differences in acclimation temperature.