Diaphragmatic eventration is an abnormal elevation of weakened hemidiaphragm due to muscular aplasia or paralysis1. Morgagni hernia represents an anterior defect of the diaphragm through the foramen of Morgagni2. Though both are uncommon, presentation might be respiratory distress, radiological features mimicking cardiomegaly or mediastinal masses2. Case presentation: A baby girl was delivered at term with 3.16kg, with normal antenatal scans. Baby developed tachypnea and peripheral cyanosis soon after delivery . Cardiovascular examination revealed a dual rhythm with normal blood pressure and pulse pressure, without audible murmurs. A chest radiograph demonstrated a markedly enlarged cardiac silhouette. 2D echocardiography (2D ECHO) excluded true cardiomegaly , revealing a non-dilated left ventricle with normal systolic function and a small patent ductus arteriosus (PDA). However, a large extracardiac mass compressing the right atrium and ventricle was noted, suggestive of diaphragmatic hernia or diaphragmatic eventration. On day 3, contrast-enhanced computed tomography (CECT) of the chest reported a rightsided anterior diaphragmatic (Morgagni) hernia with an approximately 3 cm defect. The infant was transferred to a tertiary pediatric surgical center for definitive repair. Intraoperatively , no true diaphragmatic defect was identified, confirming the diagnosis of right diaphragmatic eventration. Surgical plication of the diaphragm was performed. The postoperative course was uneventful. Conclusion: When evaluating neonates with apparent cardiomegaly and extracardiac thoracic masses, a high index of suspicion for diaphragmatic eventration should be maintained as diagnostic limitations of imaging modalities are associated. Prompt surgical management can result in excellent outcomes2. Keywords: Diaphragmatic eventration; Morgagni hernia; Neonate; Cardiomegaly mimic; Pulmonary hypoplasia