Prenatal diagnosis of pulmonary arteriovenous malformations (PAVM), caused by abnormal communications between pulmonary arteries and pulmonary veins, is rarely described. We report a case of a PAVM between the right pulmonary artery and the left atrium, referred to our prenatal unit at 22 + 1 weeks of gestation, with severe cardiomegaly, dilation of the right pulmonary artery and a right pulmonary vein and retrograde flow in the ductus arteriosus. The fistula was located in the right lung and showed a broad, disturbed flow at color Doppler with high velocity and low pulsatility. The fetus was monitored weekly and cardiac function remained sufficient until 36 + 1 weeks of gestation, when increasing cardiomegaly prompted delivery by cesarean section. The newborn was transferred to the neonatal intensive care unit, intubated and the fistula was surgically removed. The boy could be discharged at the 43rd day of life and showed an uneventful course until the last follow-up at the age of 4 years, with no residual mental or physical handicaps and a normal cardiac function. Despite adverse outcomes described in previously reported cases of large PAVM complicated by severe cardiomegaly at midtrimester scan, our case had a good outcome.