Background: Ionizing radiation absorption causes immediate biochemical, sub cellular and cellular damage, while its morphological expression and organ dysfunction are often considerably delayed. This study was aimed to investigate the possible therapeutic effects of ethanolic olive leaves extract or bone marrow derived-mesenchymal stem cells (BM-MSCs) transplanted in the liver of rats exposed to gamma radiation. For this purpose, hematological and biochemical parameters were determined Materials and methods: 50 adult male albino rats (Sprague dawely strain) were used in this study. They were divided into 5 groups (C group: Untreated control rats; R group: rats exposed to a single dose of gamma-radiation (6 Gy), OLE group: rats treated with olive leaves extract (15 mg /kg body weight / day for 30 days), R+OLE group: animals of this group were irradiated with 6Gy then treated with OLE(15 mg /kg body weight/ day) after 3 hours post irradiation for 30 days. and R+MSCs group: Mesenchymal stem cells-irradiated animals (MSCs +R): animals of this group were irradiated with 6Gy then injected after 6hours post irradiation with (BM-MSCs) 3×10 6 cells/ml suspension through caudal vein. All these groups were subjected to hematological and biochemical investigations. Results: Hematological and liver function changes were shown in gamma irradiated rats, these changes included a significant depression in hematological parameters of blood such as (RBCs, Hb, Hct and WBCs)and a significant increase in liver parameters (ALT,AST and ALP) at different intervals of the experiment in comparison with the control group. These changes manifested good amelioration in the exposed groups by using either olive leaves extract (OLE) or bone marrow mesenchymal stem cells (BM-MSCs). Conclusion: Ethanolic olive leaves extracts and mesenchymal stem cells have ameliorated hematological and biochemical parameters changes in liver of the irradiated group. their actions may be due to their anti-inflammatory and antioxidant properties.