We evaluated the combined effect of temperature (20–3450%) on growth and serum glucose, triglyceride, and total protein levels in GIFT tilapia juveniles. We used a central composite rotatable experimental design and response surface methodology. The entire experiment lasted for 8 weeks. The linear effects of temperature, dietary protein level on growth and feed utilization were statistically significant (<0.05). High temperatures and high dietary protein levels inhibited specific grouth rat (SGR) and feed efficiency (FE). The linear effects of water temperature on serum glucose, triglyceride, and total protein levels were statistically significant (<0.05). At a dietary protein level of 37.5%, serum glucose levels increased gradually as water temperature increased, whereas serum triglyceride and total protein levels decreased at the beginning and increased thereafter. The linear effect of dietary protein levels on serum glucose levels was significant (<0.05); but the linear effect on serum triglyceride and total protein levels was insignificant (>0.05). The reciprocal effects of temperature×dietary protein levels on FE, serum glucose, triglyceride, and total protein levels were significant (<0.05). SGR, FE, serum triglyceride, and total protein levels than by owever, the pattern was reversed for serum glucose levels. Using our data, we developed a model to describe the effect of temperature and dietary protein level on serum glucose, triglyceride and total protein levels. The coefficients of determination were ), and could be applied in projection. The optimal temperature/dietary protein level combination, obtained using a statistical optimization approach, was 29.9The respective effects of water temperature on serum glucose, triglyceride, and total protein levels were observed under different dietary protein levels. Increased water temperature contributes to the better use of dietary protein, and an increase in serum protein catabolism and conversion.