Background and aimsAmong the factors associated with cancer are the oxidative stress and increased expression of some microRNA (miRs). Silibinin has an anti-tumor effect. Therefore, this study evaluates the effects of silibinin on oxidative stress indices and miR-10b expression in the animal models of breast cancer.Material and methodsIn this study, 48 Balb/c mice were divided into six groups (each group contains eight mice): the healthy control, the cancer control, the healthy group receiving 20 mg of silibinin, the cancer group receiving 20 mg of silibinin, the cancer group receiving 40 mg of silibinin and the cancer group receiving 80 mg of silibinin for three weeks. In order to induce cancer, 4T1 cell line was used. After obtaining breast tumor samples, the levels of Malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX) and miR-10b expression in breast tumor biopsy were evaluated. Data were analyzed using one-way ANOVA, Kruskal–Wallis, Mann–Whitney and t-test (p<0.05).ResultsThe use of silibinin at different doses increased the activity of SOD and GPX (significantly) and the level of TAC (significantly) in the treatment group compared to untreated cancerous mice, but mir-10b and MDA were decreased non-significant and significantly respectively.ConclusionSilibinin led to a non-significant reduction of miR-10b in the treatment group compared to untreated cancerous mice. Silibinin has been shown to improve oxidative stress in breast cancer mice.