Background: MicroRNA-206 (miR-206), a muscle-specific miRNA, regulates the growth of cardiac myocytes and pulmonary artery smooth muscle cells. However, it remains unknown whether miR-206 is involved in pulmonary hypertension (PH) due to left heart diseases (PH-LHD). This study was designed to investigate the correlation between miR-206 and PH in patients with LHD. Methods: In 82 consecutively enrolled LHD patients, we examined the serum levels of miR-206 and analyzed its correlations with pulmonary artery systolic pressure (PASP) and cardiac function. Another 36 age- and sex-matched subjects served as healthy controls. Results: The patients were divided into the LHD group (n=47, PASP<50 mmHg) and the PH-LHD group (n=35, PASP≥50 mmHg). The level of miR-206 was significantly decreased in the PH-LHD group compared with that of the LHD and healthy control groups. In addition, the miR-206 level was correlated with PASP (r=-0.305, p<0.001) but not with systemic blood pressure. Univariate analyses showed that miR-206, brain natriuretic peptide (BNP), left ventricular ejection fraction and left atrial longitudinal diameter (LAD) were significantly related to PASP. Multivariate regression analysis identified miR-206 as an independent predictive factor for PH. MiR-206 alone (cut-off <0.66) demonstrated a sensitivity of 68.60% and a specificity of 65.80% in predicting PH. Moreover, the combination of miR-206, BNP and LAD (cut-off 0.21) showed a sensitivity of 97.10% and a specificity of 80.30% in predicting PH in LHD patients. Conclusion: A decreased circulating miR-206 level was associated with increased PASP in LHD patients. Thus, the level of miR-206, especially combined with BNP and LAD, might be helpful in the detection of PH in LHD patients.