Objective To establish a tree shrew mode of breast tumor. Method Forty-five 3 to 4 month-old female tree shrews were orally gavaged with 20 mg 7, 12-dimethylbenz(a)anthracene (DMBA) or peanut oil per animal for three times. Following that, fifteen DMBA administrated tree shrews were implanted 90 day-release medroxyprogesterone acetate (MPA) pellets. The tree shrews were palpated once weekly to detect mammary tumors for 45 weeks after first DMBA administration. Results DMBA were able to induce breast tumors (12.5%) in tree shrews, and MPA increased the tumor incidence (50%) while no breast tumors were observed in the control group. Three induced breast tumors were intraductal papillary carcinomas and one was IDC by H&E stain. Conclusion All induced tumors are similar with spontaneous tumors in structure and molecular markers.