The ever-increasing number of different miRNAs and their association with a vast number of cellular dysfunctions and diseases have initiated several groups to investigate miRNA maturation, which ultimately leads to down regulation of a target messenger RNA (mRNA) and its downstream product. A rapid, convenient, and reliable assay to detect the Dicer-mediated miRNA-maturation step may facilitate research in this field. Here we describe the in vitro detection of the Dicer-mediated miRNA maturation step using unmodified pre-miRNA and branched rolling circle amplification.