Pulmonary arterial hypertension (PAH) is associated with sustained vasoconstriction, profound structural remodeling of vasculatures and alterations in Ca2+ homeostasis in arterial smooth muscle cells (SMCs), while the underlying mechanisms are still elusive. By regulating the expression of proteins, microRNAs (miRNAs) are known to play an important role in cell fates including differentiation, apoptosis and proliferation, and may be involved in the development of PAH. Based on our previous study, hypoxia produced a significant increase of the miR-190 level in the pulmonary artery (PA), here, we used synthetic miR-190 to mimic the increase in hypoxic conditions and showed evidence for the effects of miR-190 on pulmonary arterial vasoconstriction and Ca2+ influx in arterial SMCs. Synthetic miR-190 remarkably enhanced the vasoconstriction responses to phenylephrine (PE) and KCl. The voltage-gated K+ channel subfamily member, Kcnq5, mRNA was shown to be a target for miR-190. Meanwhile, miR-190 antisense oligos can partially reverse the effects of miR-190 on PASMCs and PAs. Therefore, these results suggest that miR-190 appears to be a positive regulator of Ca2+ influx, and plays an important role in hypoxic pulmonary vascular constriction. J. Cell. Biochem. 115: 1196–1205, 2014. © 2013 Wiley Periodicals, Inc.