We report a case of right-sided aortic arch with isolation of the left subclavian artery diagnosed using computed tomography (CT). This was a rare type in which the left subclavian artery, originating from the pulmonary artery via the arterial duct, was isolated after closure of the ductus. Collateral circulation was considered to be obtained mainly from the left intercostal artery via the costocervical trunk through the supreme intercostal artery.