Vitamin C (VC) is an essential water-soluble antioxidant vitamin involved in normal physiological functions in fish. It plays important roles in growth, collagen synthesis, iron metabolism, and immune function. VC has also been found to play an active role in reducing the effects of pre-slaughter stress and in improving the meat quality of livestock and poultry. However, little information is available on its effect on flesh quality in the genetically improved farmed tilapia (GIFT), Hence, this study was conducted to investigate the effects of dietary supplemental VC on growth, flesh quality and antioxidant function in GIFT, 77.07±2.24 g) were assigned to four groups (20 fish per replicate, triplicate experiments). The fish were fed four experimental diets supplemented with different levels of VC: 0300 and 1 500 mg/kg (C 0, C 60, C 300 and C 1500, respectively), supplied as L-ascorbyl-2-phosphate for 56 d. After the feeding trial, fish fed with the C 0 diet had significantly lower weight gains, specific growth and survival rates than those fed on diets supplemented with VC (<0.05), but no significant differences were observed among fish fed on diets supplemented with VC (>0.05). Dietary VC supplementation had no significant effect on the protein, lipid and ash contents of fish muscle (>0.05). However, the moisture content of fish muscle in the C 1500 group was significantly lower than those in the other three groups (<0.05). Fish fed the C 300 diet had significantly higher springiness and chewiness than those fed on the C 0 diet (<0.05). The values for hardness, cohesiveness, springiness, gumminess, and chewiness of the fish fed on the C 1500 diet were significantly higher than those of fish fed the C 0 diet (<0.05). However, muscle resilience was not significantly affected by dietary VC levels (>0.05). VC supplementation increased the superoxide dismutase activity in the serum and muscle tissue of tilapia significantly (<0.05). Fish fed with the C 300 diet had the highest serum peroxidase activitysignificantly higher than that of the C 0 group (<0.05). Compared with the C 0 group, peroxidase activity in muscle increased but was not significantly different from the VC-supplemented groups (>0.05). The malonic aldehyde contents in serum and muscle decreased significantly in the VC-supplemented groups and the C These results suggest that dietary VC supplementation (at an effective level of 282 quality and antioxidant function, it is recommended to supplement 1 500 mg/kg VC (at an effective level of 1 437 mg/kg) in the diet of GIGT.