Breast cancer is the leading cause of cancer-related death in women. Positive outcomes are largely due to the success of treatments targeting hormone receptors in hormone receptor-positive disease. However, a significant fraction of cases develops resistance and progress to metastatic disease. At the molecular level, disruptions of cell type-specific enhancers and their associated transcriptional programs play key roles in tumorigenesis. In breast cancer, many frequently mutated genes encode epigenetic regulators. Therefore, a deeper understanding of the underlying molecular mechanisms is required to uncover novel therapeutic targets and develop new drugs for treating estrogen receptor (ER)-positive breast cancers. Recently, we have identified a non-canonical role for Argonaute1 (AGO1) as a coactivator of estrogen-induced enhancers. ChIP-seq analysis showed that AGO1 colocalizes with a vast majority of these enhancers in MCF7 cells (an ER+ breast cancer cell line) in an estrogen-dependent manner. Co-immunoprecipitation assays revealed that AGO1 interacts with ERα and RNA Pol II upon estrogen (estradiol, E2) treatment. Furthermore, AGO1 modulates the recruitment of ERα to induced enhancers, activates enhancer transcription, stabilizes induced enhancer-promoter interactions, and activates target promoters in response to E2. Overall, these results suggest that AGO1 plays a critical role in the activation of estrogen-induced enhancers. Thus, it is tempting to hypothesize that AGO1 is a key determinant of estrogen-induced enhancers with potential as a “druggable” target to improve the treatment of ER+ breast cancer.