Few studies have examined the relationship between echocardiographic indices of right ventricular (RV) function and the severity of pulmonary disease, or their prognostic impact. We evaluated the RV function in patients with interstitial pneumonia and its prognostic impact at each stage of disease severity.A total of 176 patients with idiopathic interstitial pneumonias (IIPs) were retrospectively enrolled and we evaluated RV function by transthoracic echocardiography. The severity of IIPs was graded according to the Goh score. The primary outcome was all-cause death.There were 55 patients in mild group (31%), 66 in moderate group (38%), and 55 in severe group (31%). Regarding RV function, RV free wall longitudinal strain and tricuspid annular plane systolic excursion (TAPSE) deteriorated with increasing severity of IIPs, but fractional area change (FAC) decreased significantly only in severe group. There were 64 all-cause deaths during the follow-up period (median 908 days). In moderate group, TAPSE [hazard ratio (HR): 0.85, 95% confidence interval (CI): 0.74-0.97, p=0.017], FAC (HR: 0.89, 95% CI: 0.83-0.96, p=0.001), and mean pulmonary artery pressure (PAP)/cardiac output (HR: 1.50, 95% CI: 1.08-2.09, p=0.015) were independent predictors of all-cause death, even after adjusting for age and log brain natriuretic peptide (BNP). On the other hand, not RV function or PAP but male sex and BNP level were associated with mortality in severe group.Among patients with IIPs, RV longitudinal function deteriorated with increasing severity of IIPs. Echocardiographic indices of RV function were independently associated with mortality in moderate-stage IIPs.