This study was designed to investigate the effect of Creatine (Cr) and Guanidinoacetic acid (GAA) as feed additives on growth performance, feed utilization and body composition of sex reversed (male) Nile tilapia (Oreochromis niloticus) fingerlings. Creatine and Guanidinoacetic acid play an important role in metabolism and can be applied in aquaculture for improving the growth performance, feed utilization and carcass composition of aquatic animals.Nile tilapia (10.4±0.4 g / fish) were fed a commercial diet (30% crude proteinand gross energy 4120.7 Kcal/kg.) supplemented with different additives of Cr and GAA (0.8 and1.2g / kg diet). Fish were randomly distributed (in triplicates) into 5 treatments (control, Cr 0.8, Cr 1.2, GAA 0.8 and GAA 1.2 g/ kg diet). Treatments were performed in 15 concrete ponds (1x4 m each). Fish were fed three times a day for 12 weeks at 4% of their body weight. The optimum growth performance, feed utilization and body composition were obtained at 1.2g GAA/ kg diet. The GAA in Nile tilapia diet was promising for enhancing the growth performance in Nile tilapia which may improve fish production. Using GAA is beneficial in aquaculture, definitely on Nile tilapia farming.