This study aimed to address the different gamma radiations doses effect on the liver and kidney function of rats: in vivo. A total of 60 healthy male Wistar-Kyoto rats were whole body gamma irradiated with Co 60 source with 0.883 cG/sec dose rate at the beginning of the experiment. The rats were randomly divided into 4 gamma-irradiation groups (25, 50, 75 and 100 Gy) The serum levels of activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT), UREA, creatinine (CREA) and uric acid (UAC) were measured using automated biochemical analyzer. The ALT, GGT, ALP values significantly decreased with the different gamma radiation doses compared with the control. The AST and UREA values significantly decreased after irradiation with 25 and 50 Gy gamma radiation doses compared with the control while it significantly increased with 75 and 100 Gy gamma radiation doses. The levels of CREA values decreased with no significant manner after the irradiation with gamma radiation doses compared with the control. The levels of UAC values significantly increased with 50, 75 and 100 Gy gamma radiation doses. The serum ALT and AST levels are common markers for hepatic toxicity: A lower amount of ALP indicates liver problems. The decreased CREA and the increased UAC levels might indicate development of nephritis and renal dysfunction. The excess UAC might be converted to crystals depositing in the tiny tubes of the kidney and causing acute kidney damage. It is proposed that oxidative stress is linked to the organ damage following exposure to ionizing radiation, and after the onset of oxidative stress, antioxidant treatment should be applied to delay or prevent the progression of damage.