Interstitial lung disease (ILD) can lead to pulmonary hypertension (ILD-PH), worsening prognosis and increasing mortality. Diagnosing ILD-PH is challenging due to the limitations of imaging methods. Right heart catheterization (RHC) is the gold standard for diagnosing PH but is limited to ILD patients considered for lung transplantation. This study assessed the usefulness of RHC in diagnosing ILD-PH in a large cohort of 105 patients followed for at least 72 months, examining hemodynamic parameters for survival analysis. We conducted an ambispective cohort study, diagnosing PH as mean pulmonary artery pressure ≥ 20 mmHg, pulmonary arterial wedge pressure <
15 mmHg, and pulmonary vascular resistance >
2 Wood units by RHC. We registered demographic, biochemical, echocardiographic, respiratory, and hemodynamic parameters for survival analyses. Using RHC, we found a PH prevalence of 84.7% among ILD patients who previously exhibited an intermediate-to-high probability of PH by echocardiography. Thirty-nine ILD-PH patients died, yielding a 5-year survival rate of 35%, whereas ILD patients without PH had a survival rate of 100%. Connective tissue disease-associated ILD and interstitial pneumonia with autoimmune features were the predominant ILD subtypes in ILD-PH patients. The ILD-PH group had worse pulmonary function, lower forced vital capacity, and more severe hypoxemia. Kaplan-Meier analyses showed significantly lower survival rates in ILD-PH patients with a 6-min walking distance <
360 m, tricuspid annular plane systolic excursion/pulmonary artery systolic pressure ratio <
0.35 mm/mmHg, venous oxygen saturation <
65%, and pulmonary artery compliance <
2.2 mm/mmHg. RHC accurately characterizes ILD-PH and provides long-term survival predictors.