Abstract: Background and Objective: The present study aimed to assess the appropriate level of replacement of fish meal with alternative protein sources in the feed fed to Oreochromis niloticus to evaluate the growth performance. Five diets were formulated. The control diet using fish meal at level 20%, other diets using 10% of fish meal and other 10% using Chlorella vulgaris algae, blood meal, hydrolyzed feather meal and rapeseed meal. Materials and Methods: One hundred and fifty Nile tilapia (21.8 g) were randomly distributed into five groups of three replicates of 15 fish/aquaria for 8 weeks. Body weight gain, feed conversion, specific growth rate, protein efficiency ratio and chemical analysis of fish body were measured. Results: No significant differences in growth performance between experimental groups were observed. There were significant decrease in ash% of whole fish body fed rapeseed meal and hydrolyzed feather meal. However, the ether extract percentage of the whole fish body fed rapeseed meal was higher than other experimental groups. No significant differences in amino acids composition of whole fish body fed the experimental diets. Conclusion: It can be concluded that fish meal can be replaced by 50% of its level with other protein sources without any negative effects on growth performance of Nile tilapia.