Studies were conducted to reveal the changes in growth, serum biochemical indices and growth hormone (GH), insulin-like growth factor Ⅰ(IGF-Ⅰ) and insulin (IN) mRNA expression abundance of Nile tilapia (Oreochromis niloticus) during fasting and re-feeding. Nile tilapia with initial body weight (62.50 ± 3.44) g were starved for 28 d and then fed for 21 d under controllable indoor environment. Fish were sampled at 0, 7, 14, 21 and 28 d during fasting and at 14 and 21 d during re-feeding, respectively. The results indicated that the body weight was significantly decreased when fasting over 7 d (P<0.05), and significantly increased when re-feeding for 21 d (P<0.05). The hepatosomatic index was significantly decreased throughout the experiment (P<0.05). Significant reduction was observed in the content of triglyceride and glucose, and in the activities of alkaline phosphatase, glutamic oxaloacetic transaminase and glutamic pyruvic transaminase after fasting (P<0.05); After re-feeding, the value of these indices increased in varying degrees, but the activity of transaminase was significantly lower than initial value(P<0.05). There was no change in total cholesterol, high density lipoprotein cholesterol or low density lipoprotein cholesterol during the experiment (P>0.05). Serum GH and liver GH mRNA levels showed significantly up-regulation, whereas significant down-regulation was observed in serum IGF-Ⅰ and liver IGF-Ⅰ mRNA levels after fasting, and after re-feeding both of them increased (P<0.05). IN mRNA level was significantly increased during fasting for 7-21 d (P<0.05), but its level was not obviously changed when fasting for 28 d (P>0.05), then was significantly decreased after re-feeding (P<0.05). The present study revealed that fasting could restrain the growth of O. niloticus, promote serum triglyceride and glucose breakdown, and decrease the activity of transaminase. Serum GH/ IGF-Ⅰ and liver GH/ IGF-Ⅰ mRNA expression abundance displayed synchronous changes and the liver IN mRNA expression abundance was significantly increased when fasting for 7-21 d and then decreased to normal level when fasting for 28 d. It suggests that the level of GH / IGF-Ⅰ gene transcription of O. niloticus may be the most important factor in determining the levels of hormone in serum, while down-regulation of serum insulin may be due to its release reduction in islet when fasting.