Abstract: MicroRNAs are endogenously expressed and highly conserved non-coding RNAs which regulate gene expressions in eukaryons. Recent studies have found that the dysregulation of some microRNAs plays an important role in pulmonary arterial hypertension (PAH) and some other cardiovascular diseases. MicroRNAs thus become novel biomarkers of these diseases and show potentials of clinical applications. This review focuses on the roles of microRNAs in PAH.