The flesh quality of Monosex Nile tilapia (Oreochromis niloticus) was examined in a research to assess the feeding effect by different red natural pigments (shrimp by-product meal (SH), red pepper meal (RP), and tomato meal (TM)) at level of 2%. Fish samples were given a pelleted meal (25% crude protein, CP), two times per day for 90 days, in a concrete tank (5×2×1 m), at a density of 10 fishes. The results showed that, as compared to the control group, fish fed diets containing various natural red pigments had considerably higher body weight, weight gain, and specific growth rate, however, the differences are statistically insignificant (P>0.05). The whole body composition of fish showed that the best treatment was fish fed a diet that contained RP compared to Ctr diet. The TBARS values of Ctr sample showed the highest value while SH recorded 0.35mg MDA/kg sample at 0 day and increased to 0.7 mg MDA/kg after 4th day of refrigerated storage at 5 ± 0.5 ºC. The highest acceptable scores of sensory parameters were given for RP fish, and the lowest was for Ctr fish. In conclusion, the red pepper or shrimp by-product meal as a source of natural pigments could promote development and feed utilization of Oreochromis niloticus diet, which reflected on quality improvement of fish skin and flesh colors beside delaying in lipid oxidation.