In Nile tilapia, the mRNA expression level of various sex differentiation-related genes can be affected by high-temperature induction during the critical period of sexual differentiation, triggering sex-reversal from female to physiological male. However, it is unknown whether the effect of high temperature on Nile tilapia () sex differentiation-related genes is period-specific. In this study, the expression of eight sex differentiation-related genes, four heat shock protein genes and two methyltransferase genes were in 8-month-old Nile tilapia under high-temperature (36) treatment by quantitative real-time RT-PCR techniques. The results showed that the expression levels of , which are ovary development-related genes, were down-regulated (, which are testis development-related genes, were not significantly changed (>0.05) under high-temperature treatment. The results differed from those for high-temperature treatment of Nile tilapia during the critical period of sexual differentiation. The expression level of DNAJB1 was significantly down-regulated. The expression levels of were not significantly changed in the gonads of females and males under high-temperature induction. Furthermore, it was also found that high temperature significantly up-regulated the expression level of in the female gonad.