BACKGROUND: This study aimed to assess patients' clinical and echocardiographic features in pulmonary hypertension (PH) due to congenital heart disease (CHD). METHODS: The main inclusion criterion was a mean pulmonary arterial pressure (mPAP) ≥ 25 mmHg measured at right heart catheterisation (RHC). All patients underwent clinical examination, electrocardiography, transthoracic echocardiogram, and a six-minute walk test (6MWT). RESULTS: Seventy-five patients with a median age of 9.98 years (IQR 7.97-17.1 years) were included. Simple ventricular septal defect (VSD) was the most common lesion. The median mPAP on right catheterisation was 52 mmHg (IQR 49-67 mmHg). Right ventricle (RV) dysfunction was observed in all patients, confirmed by prolonged right ventricular MPI, reduced S', decreased TAPSE, and impaired calculated RV free wall strain. The pulmonary valve annulus was markedly dilated in all patients, evidenced by a median z-score of 4.23. The combination of using the RVSP of more than 50 mmHg plus a pulmonary annulus z-score of more than 3 to predict PVR of more than 3 Wood units m² had a high sensitivity of 82.4% but a low specificity of 14.3%. CONCLUSION: Our patients exhibited dilation on the right side, especially the pulmonary arteries, which could serve as an early warning for PH. An elevated peak RVSP and a dilated pulmonary artery should alert the physician to the possibility of PH. An echocardiogram should only be used as a screening tool for diagnosing pulmonary hypertension.