This experiment was performed to determine the effects of dietary ascorbic acid (ASA) supplementation oil blood components, leukocyte and tonic immobility of male turkeys under summer conditions. A total of 120 one-day-old male turkeys were fed with three different diets. The experimental diets were: control without ASA (ASA-0), 150 mg of ASA/kg (ASA-150) and 300 mg of ASA/kg (ASA-300) of diet. The turkeys received the experimental diets for IS weeks. Diets ill mash form and water were provided ad libitum. In the ASA-150 and ASA-300 groups, the eosinophile and basophile ratios were higher than those of the ASA-0 group at 12 weeks of age (P < 0.05 and P < 0.001), but lymphocyte (L), heterophil (H), monocyte, H: L ratio and tonic immobility were not influenced by the ASA levels (P > 0.05). Both dietary ASA levels caused a quadratic decrease in serum cholesterol, low density lipoprotein (LDL) and glutamic-oxaloacetic transaminase (SGOT) (P < 0.05), whereas dietary ASA caused a finer increase in serum iron concentration of turkey. (P < 0.05). Serum glucose, triglyceride, high density lipoprotein (HDL), total protein, albumin. globulin. lactate dehydrogenase (LDH), glutamic pyruvate transaminase (SGPT), urea, Uric acid and alpha amylase were not affected by the addition of ASA to the diets (P < 0.05). As a conclusion, blood haematological profile, serum biochemical components and tonic immobility of turkeys were not significantly affected by dietary ASA levels at chronic high summer temperatures in general. and, therefore, there is no need for ASA supplementation in turkeys' diets under summer temperatures that do not exceed 31.7 degrees C.