BACKGROUND SOX7 exerts a repressing effect against tumors and imposes vital influences on malignancies. Our research discussed the importance of SOX7 in breast cancer prognoses. MATERIAL AND METHODS SOX7 mRNA expression in breast cancer tissues samples and matched adjacent normal controls of breast cancer patients was measured by quantitative real-time-polymerase chain reaction (qRT-PCR). The relationship of SOX7 with clinicopathological characteristics were analyzed via chi-square test. The association of SOX7 levels with clinical outcomes was evaluated adopting the Kaplan-Meier method and multivariate Cox proportional hazards regression model. RESULTS SOX7 mRNA degree of expression exhibited a declining tendency in breast cancer tissue compared to paired bordering normal tissue specimens (P<0.001). In addition, the reduced SOX7 degree of expression had a strong correlation to larger cancer mass dimension (P=0.006) and lymph node metastasis (P=0.001). Survival analysis revealed that the overall survival (OS) time was much shorter among cases harboring low SOX7 degree of expression compared to high degree of expression (P=0.005). Moreover, SOX7 expression alone could predict OS among breast cancer patients (hazard ratio=3.956, 95% confidence interval=1.330-11.772, P=0.013). CONCLUSIONS SOX7 expression was downregulated in breast cancer tissues, and it could function as a useful prognostic marker in breast cancer.