The present study was designed to evaluate the use of Spirulina, Arthrospir platensis as a protein source for hybrid red tilapia fries (Oreochromis niloticus x Oreochromis mossambicus) with average weights of 206±11 mg. Spirulina was incorporated into diets at 0, 50, 75, and 100% of the fishmeal-based diet. The test diets were fed to the fish at 12% body weight three times a day for consecutive 65 days at 24±2°C. The final weight gain, specific growth rate, feed conversion ratio (FCR) and survival rate of fish were evaluated. The present study suggests that up to 75% of Spirulina can be substituted for fishmeal in a fishmeal-based diet for hybrid red tilapia with increased feed conversion ratio and protein productive value in carcass proximate composition. Also higher immunity can be observed than other treatments, where white blood cells were 4.08 x10 3 mm. In conclusion, the results of this study indicate the possibility of using Arthrospira platensis as commercial nutrient source for large scale culture of fish in general and tilapia in particular.