ERRα is an orphan nuclear receptor emerging as a novel biomarker of breast cancer.Over-expression of ERRα in breast rumor is considered as a prognostic factor of poor clinical outcome.The mechanisms underlying the dysexpression of this nuclear receptor, however, are poorly understood.MicroRNAs (miRNAs) regulate gene expression at the post-transcriptional level and play important roles in tumor initiation and progression.In the present study, we have identified that the expression of ERRα is regulated by miR-137.