Background: The main purpose of this study was to investigate whether or not electron beam therapy (EBT) was an effective method in terms of moderating oxidative stress by reducing free radicals in BALB/c mice with type 1 diabetes mellitus.Methods: The study was performed on thirty BALB/c mice in three groups including normal control, diabetic control, and EBT treated. Before studying the effect of electron beam on the studied groups, optimal level of constant source-to-surface distance, as well as the effects of EBT on glutathione reductase (GR) structure and function were determined. After studying the structure and the function of GR protein with three methods including fluorometry, circular dichroism (CD), and activity assay methods, SSD 100 was selected for EBT. Glucose, advanced glycation end-products, GR, oxidative stress factors such as hydrogen peroxide, malondialdehyde, advanced oxidation protein products, oxidized low-density lipoprotein, and inflammatory factors were measured in the serum of all groups.Results: The results of in vitro study showed that electron beam therapy could increase glutathione reductase activity, which was not significant. Also, the results were compared between and within groups using one-way analysis of variance. Significant differences were observed for all variables measured between the normal control group and the other groups (P < 0.05). There was also no significant difference in blood glucose levels between the electron beam therapy treated group and the diabetic one (P > 0.05).Conclusion: The results suggested that electron beam therapy could be effective in reducing free radicals and oxidative stress. Electron beam therapy, as a complementary method, might aid in moderating the complications of diabetes mellitus.Keywords: Diabetes mellitus, Electron beam, Inflammatory factors, Oxidative stress