Migration and invasion enhancer 1 (MIEN1) is a membrane-anchored protein that is highly expressed in various types of cancer, and is correlated with the PI3K/AKT pathway. The aim of this study was to investigate the expression of MIEN1 and its clinical pathological significance in breast cancer. We used immunohistochemical staining to examine the expression of MIEN1 in 40 samples of human breast cancer tissue and 10 samples taken from regions adjacent to normal breast tissue. The rate of detection of MIEN1 protein was 67.5%, which was significantly higher than that in adjacent non-cancerous breast tissue (0%, P < 0.05). The expression of MIEN1 correlated with age, World Health Organization grade, and lymph node metastasis, but not with tumor size or family history of cancer. Kaplan-Meier survival analysis showed that patients with positive MIEN1 protein expression had a lower overall survival rate than patients who did not express MIEN1. Downregulation of MIEN1 suppressed the expression of matrix metallopeptidase 9 by downregulating the expression of protein kinase B (also known as AKT) in breast cancer cells. Our results indicate that MIEN1 overexpression may facilitate migration and invasion in breast cancer, and MIEN1 is a potential molecular target for cancer chemotherapy.