According to several previous reports on persistent fifth aortic arch (PFAA), the presentation of the patients was usually either very mild when diagnosed by physical examination including upper body systemic hypertension and systolic murmur, or severe with ductal shock in the neonatal period. In our case, the clinical course was unique with relatively mild narrowing at the distal PFAA and an interrupted fourth aortic arch. It can be classified as medium severity based on the timing of presentation to the hospital. In the present case, severe LV dysfunction suggested sustained narrowing at the junction between the PFAA and the descending aorta and insufficient development of collateral arteries.We experienced a case with PFAA with severe LV dysfunction. These findings suggest another differential diagnosis for severe LV dysfunction in infancy.