Objective: To investigate clinicopathological features, immunophenotype, diagnosis and differential diagnosis of ovarian Brenner tumors. Methods: Clinical data, histological morphology, and immunophenotype of 21 cases of ovarian Brenner tumors were retrospectively analyzed, and the related literature was reviewed. Results: All 21 cases of ovarian Brenner tumors were adult women, with an average age of 52 (28 to 76) years. Among them, 13 cases (61.9%) were postmenopausal and 8 cases (38.1%) were premenopausal. There were 16 cases of cystic and solid masses and 5 cases of solid masses. Eighteen cases (85.7%) of the Brenner tumors were benign, 2 (9.5%) were borderline and 1 (4.7%) was malignant. Usual tumor markers of ovarian carcinoma, including CA199 and CA125 were normal or only slightly elevated in 21 cases. Imaging before surgery was not specific to ovarian Brenner tumors. Microscopically, benign Brenner tumors were composed of dense fibrous stroma and scattered nests of transitional-type cells. In borderline Brenner tumors, besides the similar morphology to benign Brenner tumors, the epithelial cell layers were increased, with different degrees of atypia and lack of stromal invasion. In one malignant case, besides the morphology of benign and borderline Brenner tumor, atypical of transitional-type cells exhibited stromal invasion. Immunophenotype: CK7, GATA3, p63 and CK5/6 were positive in tumor cells, Uroplakin III was expressed in a few cases, while WT-1, Pax-8 and CK20 were negative. Ki-67 was less than 3% in benign tumors, 5%–10% in borderline tumors and 50% in malignant tumor. Conclusion: Ovarian Brenner tumors are rare epithelial ovarian tumors. Preoperative imaging examinations and usual ovarian tumor markers do not provide definite diagnostic value. Diagnosis and classification of Brenner tumors depend on histopathological evaluation and immunohistochemical staining. The key to differentiate benign and malignant Brenner tumors is the degree of tumor cells atypia and stromal invasion.