Surgical or medical closure of a patent ductus arteriosus (PDA) is a very common practice in premature infants in the neonatal intensive care unit, but often the coronary arteries are not delineated prior to closure. In this report, a 32-week gestational age premature infant who underwent surgical ligation of a PDA developed new-onset left ventricular systolic dysfunction. A repeat echocardiogram noted an anomalous left coronary artery from the pulmonary artery. Successful left coronary artery reimplantation with rapid normalization of left ventricular systolic function occurred. As previously not reported, ligation of a PDA in a premature infant can unmask anomalous left coronary artery from the pulmonary artery. Surgical left coronary artery reimplantation is the mainstay of therapy and should be performed to establish normal coronary blood flow, even in a premature, low birth weight infant.