Abstract: Objective: The present study was designed to investigate the hepatic and renal toxicity of acephate (ACE) insecticide in broiler chicks by studying the hematological, biochemical, oxido-inflammatory and pathological changes after subacute exposure to ACE in diet and to evaluate the modulatory role of flaxseed oil (FSO) on these changes. Materials and Methods: Two hundred and forty day-old un-sexed broiler chicks (average body weight of 45.52±0.25 g) were randomly assigned into 4 groups with 4 replicates of 15 chicks based on a completely randomized design. The first group was fed a basal diet, 2nd group fed basal diet supplemented with 85.2 ppm acephate, while the 3rd group fed basal diet supplemented with 1000 ppm flaxseed oil, while the 4th group fed basal diet supplemented with 85.2 ppm ACE+1000 ppm FSO for 4 weeks. Results: The ACE significantly (p<0.05) decreased hemoglobin content, erythrocytic count and packed cell volume while increased white blood cells, lymphocyte and granulocyte counts. Moreover, there was a significant increase in lipid profile (total cholesterol, LDL and triglyceride) and serum biomarkers related to hepatic and renal functions including aspartate transaminase (AST), alanine aminotransferase (ALT), urea and creatinine with no change in alkaline phosphatase (ALP) and albumin while, serum total protein, globulin and HDL-cholesterol levels were significantly reduced with ACE group in comparison with other treatment groups. The ACE significantly (p<0.05) decreased the antioxidant capacity of liver and kidney and increased lipid peroxidation, interleukine-2 (IL-2) tumor and necrosis factor-alpha (TNF-α) in the two organs while increased the activity of cytochrome P450 in liver only. Diet supplemented with FSO showed promising modulatory effects on these undesirable changes however, some did not restored to normal levels. Conclusion: It is recommended to use FSO regularly as a dietary supplement for broiler chicks to provide them powerful antioxidants required to protect these birds against environmental pollution.