Breast cancer susceptibility gene 1 (BRCA1) located at chromosome 17q12-21 is a classic tumor suppressor gene, and has been considered as a significant role in hereditary breast cancers. Moreover, numerous studies demonstrated the methylation status of CpG islands in the promoter regions of BRCA1 gene was aberrant in patients with sporadic breast tumors compared with healthy females or patients with benign diseases. However, these conclusions were not always consistent. Hence, a meta-analysis was performed to get a more precise estimate for these associations. Crude odds ratio with 95% confidence interval were used to assess the association of BRCA1 promoter methylation and the risk or clinicopathologic characteristics of breast cancers under fixed or random effect model. A total of 40 studies were eligible for this present study. We observed the frequency of BRCA1 promoter methylation was statistically significant higher in breast cancers than non-cancer controls. Furthermore, BRCA1 methylation was statistically associated with lymph node metastasis, histological grade 3, ER(-), PR(-), triple-negative phenotype, and decreased or lack levels of BRCA1 protein expression. In conclusion, this study indicated that BRCA1 promoter methylation appeared to be a useful predictive or prognostic biomarker for breast cancers in clinical assessment.