Myelination of axons by oligodendrocytes and Schwann cells in the central and peripheral nervous system, respectively, is essential for normal neuronal functions, and its failure results in devastating demyelinating diseases. During development, both oligodendrocyte and Schwann cell precursors undergo a temporally well-defined series of molecular and structural changes, ultimately culminating in the cessation of proliferation and the elaboration of a highly complex myelin sheath. Recent studies have demonstrated a critical role of microRNAs (miRNAs) in the progression of oligodendrocyte and Schwann cell precursors to the myelinating state—depletion of miRNAs from either cell type results in an arrest in differentiation and lack of myelination. Furthermore, these studies have begun to elucidate the dynamic regulation of miRNA expression and the complexity of miRNA-mediated gene regulation during differentiation of myelinating cells. In this review, the authors highlight the recent understanding of functional links of miRNAs to regulatory networks for central and peripheral myelination, as well as perspectives on the role of miRNAs in demyelinating diseases.