The overexpressed in lung cancer 1 (OLC1) has been demonstrated to be associated with numerous biological and pathological processes. However, the role of OLC1 in breast cancer has not been thoroughly elucidated. The purpose of this study was to assess OLC1 expression and to explore its contribution to the breast cancer. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was conducted to detect OLC1 messenger RNA (mRNA) expression in 45 pairs of fresh-frozen breast cancer tissues and corresponding noncancerous tissues. Immunohistochemistry was performed to detect the expression of OLC1 in 145 breast cancer tissues. The relationship between the expression of OLC1 and clinicopathological characteristics and prognosis was statistically analyzed. We found that the expression levels of OLC1 mRNA and protein in breast cancer tissues were significantly higher than those in adjacent noncancerous tissues (P < 0.001). In addition, OLC1 expression was significantly correlated with tumor size (P = 0.034), grade (P = 0.015), stage (P < 0.001), and lymph node metastases (P = 0.028). Kaplan-Meier survival analysis showed that a high expression level of OLC1 resulted in a significantly poor prognosis of breast cancer patients. Further, Cox multivariate analysis indicated that OLC1 expression level was an independent prognostic factor for the overall survival rate of breast cancer patients. These findings provide evidence that a high expression level of OLC1 serves as a biomarker for poor prognosis for breast cancer. Thus, we speculate that OLC1 may be a potential target of antiangiogenic therapy for breast cancer.