Immunotoxicity for subacute exposure to acephate (O,S-dimethyl-acetylphosphoramidothioate) was assessed in day old White Leghorn (WLH) cockerel chicks. The chicks were divided into five groups. Groups C1 and C2 served as plain control and vehicle control respectively. Chicks of groups T1, T2 and T3 were administered acephate suspended in groundnut oil at 21.3mg/kg, 28.4mg/kg and 42.6mg/kg respectively orally for 28 days. A non-significant reduction in total leukocyte count was observed. Although, anti-Newcastle Disease Virus (NDV) antibody titer, serum total protein (TP), serum globulin, serum albumin and organ:body weight ratios of immune organs were significantly suppressed. The delayed type hypersensitivity response to 2,4-dinitro-1-chlorobenzene (DNCB) was not significantly altered. Histopathologically, bursa and spleen showed mild depletion of lymphocytes. Furthermore, DNA fragmentation assay was performed and detected ladder pattern (180bp) in DNA. It was concluded that subacute acephate exposure at low concentrations may affect immune responses in avian species.