Objective: This study investigated the antioxidant effect of coenzyme Q10 on ionizing radiation induced oxidative damage in pancreatic β-cells. Methods: Twenty-four male rats were assigned to 4 groups. Group 1 constituted the control group, Group 2 only received a single i.p. dose of coenzyme Q10, Groups 3 and 4 received a total of 4 Gy external x-ray radiation to the abdomen in a single fraction. Group 4 also received a single dose of 200 mg/kg coenzyme Q10 i.p. 30 minutes prior to x-ray irradiation. Results: The x-ray radiation group showed decreased β-cell positivity in the islets of Langerhans com pared to the control group on immunohistochemical analysis. In contrast, an increase in β-cells exhib iting insulin positivity was observed in group 4 (ionizing radiation+coenzyme Q10) compared to the irradiation group. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay indicated a rise in the number of apoptotic cells in the x-ray radiation group compared to the control and coenzyme Q10-only groups (Group 2). Meanwhile, we observed a decrease in the number of terminal deoxy nucleotidyl transferase dUTP nick end labeling-positive apoptotic cells in the islets of Langerhans in the ionizing radiation+coenzyme Q10 treatment group (Group 4) relative to the irradiation group. Conclusion: This study shows that coenzyme Q10 reduces apoptosis in the rat pancreas exposed to abdominal ionizing radiation.