Dysregulation of miRNAs can contribute to the aetiology of diseases including pulmonary arterial hypertension (PAH). Here we investigated a potential role for the miR-214 stem loop miRNA and the closely linked miR-199a miRNAs in PAH. All 4 miRNAs were upregulated in the lung and right ventricle in mice and rats exposed to the SU 5416 hypoxia model of PAH. Further, expression of the miRNAs was increased in PASMCs exposed to TGF-β1 but not BMP4. We then examined miR-214-/- mice exposed to the SU 5416 hypoxia model of PAH or normoxic conditions and littermate controls. There were no changes in systolic right ventricular pressure or remodelling observed between the miR-214-/- and WT hypoxic groups. However, we observed a significant increase in right ventricular hypertrophy in hypoxic miR-214-/- male mice compared to controls. Further, we identified that the validated miR-214 target phosphatase and tensin homolog was upregulated in miR-214-/- mice. Thus, miR-214 stem loop loss leads to elevated right ventricular hypertrophy and may contribute to the heart failure associated with PAH.