The present study was carried out to study the effect of supplementation of Nile tilapia (Oreochromis niloticus) diets by increasing levels (0.5, 1.0 and 1.5%) of two organic acids (malic acid + oxalic acid, 1:1) blend and two organic acid salts (calcium lactate + sodium acetate, 1:1) blend. Therefore 7 diets were formulated (three diets for each blend and the control diet). Growth performance, feed utilization, some hematological parameters and proximate analysis of fish were determined after 90 days. Results could be summarized as follows: Supplementation of the basal diet by each of malic+oxalic acids blend or Na-acetate+Ca-lactate blend significantly improved the final body weight (BW), body length (BL), weight gain (WG) and specific growth rate (SGR) of Nile tilapia compared with the control diet. Fish fed the diet supplemented by 1% malic+oxalic acids blend showed the highest BW, BL, WG and SGR compared with control and the other treated fish groups and the same trend was also observed for feed intake, feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish fed the diet D4 (supplemented by 1.5% malic+ oxalic) showed the highest serum protein content while control group showed the highest level of total lipids compared with the other treatments. Fish group fed D5 (0.5% of 1:1 Na-acetate + Ca-lactate blend) showed the highest protein and ash content and the lowest lipid content of the whole fish body, whereas control group showed the lowest protein and the highest fat content.