This study evaluated the quality of the visualization of extracardiac thoracic vessels by magnetic resonance angiography (MRA) in young infants with congenital heart disease. Echocardiography is often sufficient in evaluating CHD in young infants. Cardiac catheterization is needed in some instances to evaluate extracardiac thoracic vessels. Extracardiac thoracic vessels can be accurately evaluated using MRA in adults and older children, but image quality in small infants may be limited. Twenty-nine magnetic resonance angiographic scans were performed at a single institution on 28 infants aged <3 months (median 6 days, range 1 to 90 days) with complex CHD in whom imaging was inconclusive by echocardiography. A blinded observer at a different institution graded (from 0 to 3) the quality of the visualization of the main, branch, lobar, and second-generation pulmonary arteries; lobar pulmonary veins; aortopulmonary collaterals; vena cavae; thoracic aorta and its branches; patent ductus arteriosus; and visceral sidedness. The results of MRA were compared with those of x-ray angiography and surgical inspection, when available. The mean image quality grade was >2 for all structures except the second-generation pulmonary arterial branches, for which it was 2. The median total scan duration was 9 minutes (range 3 to 46). Findings were concordant with surgical inspection (n = 25) and cardiac catheterization (n = 8) in all subjects. There were no complications. In conclusion, MRA is excellent for the visualization of extracardiac thoracic vessels in young infants with CHD and can be used as an alternative to cardiac catheterization when echocardiography is inconclusive.