An intrathoracic mass, which persisted during the remaining pregnancy, was first seen during routine ultrasound examination performed at 20 weeks gestation. After birth, the child was asymptomatic. Echocardiography showed the mass to be located intrapericardially. The mass was electively resected via sternotomy 3 weeks after the birth. Microscopic examination showed normal lung tissue surrounded by pleura corresponding to the diagnosis of extralobar pulmonary sequestration. To the authors' knowledge, this is the earliest described detection of such a lesion. Furthermore, this article reports the unique finding of a feeding vessel from the right pulmonary artery.