Abstract Background Eisenmenger syndrome is a constellation of symptoms that arise from an uncorrected large congenital heart disease that have a reversed shunt to right to left. Eisenmenger syndrome in pregnancy is rare because pregnancy in this patient is not recommendeed due to high mortality for mother and baby. The objective of this case report is to highlight the argument of Eisenmenger syndrome in pregnancy. Case Summary A 38-years pregnant woman presented to the emergency room with dyspnea since the third trimester. Reported history of the untreated ventricular septal defect. Central cyanosis, systolic murmur and lower extremity oedema were found. ECG showed a right axis deviation with right ventricular hypertrophy. Cardiomegaly was found from a chest x-ray. Left ventricular diastolic dysfunction, large ventricular septal defect with Right-Left shunt, and pulmonary hypertension were found from echocardiography. Based on characteristic appearance, a diagnosis of Eisenmenger syndrome was made. Caesarean delivery was performed and the baby delivered safely, but the mother passed away. Discussion Eisenmenger syndrome in pregnancy comes with high mortality to mother and baby. A ventricular septal defect is a common cause of Eisenmenger syndrome. The choice for medical treatment from Eisenmenger syndrome in pregnancy is still controversial. Both caesarean section and vaginal delivery could be harmful to the patient due to vulnerability to hemodynamic change.