Adrenomedullin has been shown to inhibit proliferation in pulmonary artery smooth muscle cells and to alleviate pulmonary artery collagen accumulation in pulmonary hypertension. We aimed to assess mid-regional proadrenomedullin level in children with pulmonary hypertension due to CHDs. The current study was conducted in the Pediatric Cardiology Unit, Tanta University Hospital, on 50 children with CHDs: twenty-five patients had a complication of pulmonary hypertension and the other 25 patients without pulmonary hypertension. Another 25 children without CHDs were concluded as a control group. We performed complete history taking, full clinical assessment, chest X-ray, electrocardiogram, and echocardiographic assessment. Plasma level of mid-regional proadrenomedullin was assessed using a sandwich enzyme-linked immunosorbent assay test. Our results showed that the mean plasma level of mid-regional proadrenomedullin was significantly increased in patients with pulmonary hypertension. Significant positive correlation was found between mid-regional proadrenomedullin and mean pulmonary artery pressure. The best cut-off point of mid-regional proadrenomedullin as a diagnostic biomarker to discriminate patients with CHDs complicated with pulmonary hypertension was 199.22 nmol/l. Mid-regional proadrenomedullin significantly increased in patients with pulmonary hypertension who died as compared to patients who survived, with the best cut-off point was 428,8 nmol/l. We concluded that plasma levels of mid-regional proadrenomedullin were significantly elevated in children with pulmonary hypertension complicated by the CHDs. It could be used as a cardiac biomarker in these patients, with good diagnostic and prognostic value.