MicroRNAs (miRNAs) are short, noncoding RNAs that posttranscriptionally regulate gene expression through altering mRNA translation and stability. Dysregulation of miRNAs has been demonstrated to alter estrogen receptor (ER) biology, through modulation of ER-alpha (ERα) signaling or regulation of ERα itself. Approximately 70% of breast cancers express ERα, and miRNA expression is demonstrated to correlate with disease status in ER-positive breast cancer. Due to the role of ERα in breast cancer development, its interaction and regulation of miRNAs have been of great interest, particularly within the context of ligand specificity and antiestrogen therapies. Here, we review the cross talk between ERα and miRNAs and their involvement in breast cancer progression, as well as resistance to endocrine therapy. We also briefly discuss the interaction of miRNAs with estrogen-related receptors (ERRs) and ERβ in mediating breast tumorigenesis.