Pulmonary sequestration (PS) is a rare congenital malformation, even more when its arterial supply is a coronary artery. We present a case of a 68-year-old man admitted in the emergency room with an acute coronary syndrome and no evidence of significant coronary disease. Instead, he had an abnormal branch from the circumflex coronary artery nourishing a mass in the left lower pulmonary lobe. A coronary steal phenomenon was proposed to explain the clinical presentation. An anterior left thoracotomy with ligation of the abnormal branch and atypical resection of the lung segment comprising the sequestration was performed.