Eggs of Pelodiscus sinensis were incubated under one fluctuating and four constant temperatures, and hatchlings from different incubation temperatures were maintained under identical conditions to assess the effects of incubation temperature on sexual phenotype and hatchling growth. The incubation length decreased as temperature increased, but it did not differ between sexes within each temperature treatment. Hatching success was higher at intermediate temperatures (28 °C, 30 °C and the fluctuating temperature regime) than at low (24 °C) and high (34 °C) temperatures. The sex ratio of hatchlings did not differ from equality within each temperature treatment. Thus, our data support previous work that P. sinensis does not have temperature-dependent sex determination, and add evidence for the prediction that turtles within the Trionychidae have genotypic sex determination exclusively. Incubation temperature affected hatchling mass, with hatchlings from intermediate incubation temperatures being heavier than those from low (24 °C) and high (34 °C) incubation temperatures. Hatching size was not a predictor of post-hatching growth. Incubation temperature affected hatchling growth, with hatchlings from 24 °C overall growing faster than did hatchlings from higher incubation temperatures. The influence of incubation temperature on hatchling growth was well buffered within the range of constant temperatures from 28 °C to 34 °C. Fluctuating incubation temperatures augmented male growth but reduced female growth, as female embryos were more vulnerable to extremely high temperatures.