Relatively high mortality has become a problem during Marsupenaeus japonicus culture in the summer in southern China. Thus, it is necessary to evaluate the thermal tolerance of M. japonicus. The upper thermal tol- erance trait (UTT) was determined to evaluate thermal tolerance of different sizes of M. japonicus. We combined the UTT with critical thermal methodology to compare thermal tolerance among three species, such as M. japoni- cus, Exopalaemon carinicauda, and Litopenaeus vannamei. We observed their behavior under gradually changing temperature and compared the lethal index. A correlation analysis revealed a correlation coefficient of −0.142 be- tween body weight and the UTT of M. japonicus. The UTT of juveniles (<0.01 g) was significantly higher than that of the group weighing 1–5 g (P<0.05). The three species responded differently to high temperature: tempera- tures for initial mortality and climax mortality of L. vannamei were highest, whereas those for E. carinicauda were the lowest. The mean UTT and critical thermal maximum of L. vannamei were highest, followed by those of M. japonicus and E. carinicauda (P<0.05). In conclusion, the thermal tolerance of M. japonicus was lower than that of L. vannamei but higher than that of E. carinicauda. These results are important data for a comprehensive un- derstanding of M. japonicus thermal tolerance and have practical applications for selecting high-temperature re- sistant strains.