Basal-like breast cancer (BLBC) appears to be characterized by a relatively unfavorable prognosis and lack of a specific therapeutic target. Estrogen receptor-alpha (ERα) has been widely accepted as a prognostic marker and a predictor for endocrine therapy response of breast cancer. This study aimed to clarify the correlation of ERα methylation with the pathogenesis and clinicopathological significance of sporadic BLBC of Chinese women without a family history of the cancer. The methylation of ERα promoter was investigated in genomic DNA of 60 sporadic BLBC with 108 cases of non-BLBC as control by methylation-specific polymerase chain reaction. We also investigated the expression of p53, breast cancer gene (BRCA)-1, and BRCA-2 by immunohistochemistry and analyzed the correlation between ERα methylation and clinicopathological features of BLBC. ERα methylation was observed in 48 of 60 (80.0%) sporadic BLBC, which was significantly higher than in sporadic non-BLBC cancer (47/108, 43.5%; χ2=20.89, p<0.01). No correlation was found between the ERα methylation and age and menopausal status, while it was significantly associated with lymph node metastasis, tumor stage, nuclear p53 accumulation, and BRCA-1 and BRCA-2 expression in sporadic BLBC. The ERα methylation status in basal-like breast cancer was significantly higher than in sporadic non-basal-like breast cancer. It was associated with the lymph node metastasis, tumor stage, p53 nuclear accumulation, and BRCA-1 and BRCA-2 expression in BLBC. It may play an important role in BLBC pathogenesis.