To investigate the association of Sirtuin 3 (SIRT 3) expression between the clinical characteristics and prognosis in breast cancer patients.308 female patients with histologically confirmed breast cancer were enrolled in this study. The SIRT 3 expressions in tumor samples were detected. All the patients were followed up overall survival time (OS) and disease-free survival (DFS) time.SIRT 3 expression was significantly correlated with clinical characteristics including lymph node metastasis, pathological grade and tumor size of breast cancer. SIRT 3 expression status also affected the DFS and OS of breast cancer. Patients with high expression of SIRT 3 had shorter DFS and OS than those with low expression. Univariate and multivariate Cox analyses confirmed that high SIRT 3 expression predicted a poor prognosis in breast cancer patient. In vitro study revealed that the SIRT 3 knockdown by small interfering RNA technique dramatically reduced the proliferation, migration and invasion of breast cancer cell lines.Our results suggest that SIRT 3 may serve as a marker for clinical feature and prognosis for breast cancer.