Prenatal diagnosis of coarctation may improve survival, but little is known regarding its association with severity of left heart hypoplasia and surgical outcome. This study compared echocardiographic measurements of left heart structures, surgical strategies, and postoperative outcomes between neonates with a prenatal diagnosis of coarctation and those with a postnatal diagnosis. All the neonates who underwent coarctation repair during 2006-2010 were reviewed. The neonates with complex congenital heart disease or an unrestrictive ventricular septal defect requiring cardiopulmonary bypass (CPB) for closure were excluded from the study. Based on the time of diagnosis, the subjects were divided into the following three groups: group 1 (prenatal diagnosis), group 2 (diagnosis at 0-7 days), and group 3 (diagnosis at 8-28 days). The study population consisted of 46 neonates: 14 in group 1, 14 in group 2, and 18 in group 3. Compared with group 3, group 1 had a smaller left ventricular volume index, lower mitral and aortic valve diameter z-scores, and lower transverse arch z-scores. Compared with group 2, group 1 had smaller aortic valve z-scores but otherwise had similar measurements. At repair, 64 % of the neonates in group 1 required CPB versus 29 % in group 2 (p = 0.12) and 22 % in group 3 (p = 0.03). All the neonates underwent biventricular repair, with no surgical mortality. Group 1 had a hospital stay of 13.4 ± 10.8 versus 7.5 ± 4.2 days in group 2 (p = 0.06) and 7.3 ± 4.5 days in group 3 (p = 0.03). The neonates with prenatally diagnosed coarctation had smaller left heart structures than the neonates with coarctation diagnosed after the first week of age, were more likely to require extensive arch reconstruction under CPB, and had longer hospital stays.