A pulmonary artery (PA) sling is a very rare congenital cardiovascular anomaly, and only a few studies have reported PA slings in fetuses. The relationship of the PA, aorta, ductus arteriosus, and trachea can be evaluated in the 3-vessel and 3-vessel and trachea views during fetal echocardiography. A PA sling can be detected by abnormal positioning of the left PA in relation to the trachea when sweeping from the 3-vessel view cranially to the 3-vessel and trachea view. Here we report 3 cases of fetal PA slings and their follow-ups. Two cases were confirmed by postnatal echocardiography, and the other case was confirmed by a cardiovascular cast after pregnancy termination. We emphasize that the 3-vessel and 3-vessel and trachea views are of crucial importance in the prenatal diagnosis of a PA sling.