The animal's need for protein resources for growth is quite expensive. Aquaculture needs a cheap protein source such as plant products. Leaves and seeds of M. oleifera have major quantities of proteins, carbohydrates, minerals and vitamins. The present study was carried out to physiologically compare the suitability of moringa seeds or leaves as a partial replacement of the total dietary protein for fish meal in practical diets for the Nile tilapia Oreochromis niloticus. For the growth experiment, four isocaloric-isonitrogenous diets contained 0, 2.92, 8.76, 14.6g/ 100g of moringa seed (MSD). Additionally, four isocaloric-isonitrogenous fermented diets (with 35g/ 100g of crude protein, and 1912.27kcal gross energy/ 100g) contained 0, 5, 10 and 20g/ 100g of moringa leaves (MLD). These diets were reared in a water-circulating system. Hematological parameters were measured, such as hemoglobin content, serum glucose, cholesterol and triacylglycerol levels. The specific growth rate of fish decreased significantly (P< 0.05) at all concentrations when fish were fed with MSD. However, when fed with MLD, the growth remained unchanged at concentrations of 5 and 10% but decreased at a concentration rate of 20% compared to the control group. The 5 and 10% replacement levels of fish meal with moringa leaves were the optimal levels for the maximum growth performance of the Nile tilapia fingerlings, but moringa seeds inhibited the growth rates of the Nile tilapia at all concentrations. Therefore, moringa leaves are suitable for fish nutrition, while moringa seeds are not recommended in food nutrition, which may be due to the presence of anti-nutritional factors and toxic substances, such as tannins, saponins, and inhibitors of trypsin.