Breast cancer is the leading cause of cancer death in women world wide which is closely related to metastasis. Recent studies argue that breast cancer cells that have undergone epithelial-to-mesenchymal transition (EMT) acquire aggressive malignant properties, but the molecular mechanisms underlying this transition are poorly understood. In this study, we found that increased expression of proline-rich protein 11 (PRR11) was associated with the progression of breast cancer and that PRR11 protein levels were significantly elevated in breast cancer. High PRR11 levels also predict shorter overall survival of breast cancer patients. Moreover, we found that the forced expression of PRR11 decreased the expression of the epithelial marker E-cadherin but increased the mesenchymal markers in breast cancer cells. In contrast, silencing PRR11 in metastatic breast tumor cells promoted a shift toward an epithelial morphology concomitant with increased expression of E-cadherin and decreased expression of mesenchymal markers. PRR11 silencing also reduced the expression of EMT-inducing transcription factors (Snail, Slug, ZEB1 and ZEB2).