Isolation of the left subclavian artery is a rare anomaly associated with acyanotic CHDs and right aortic arch. This condition can be asymptomatic or can present with neurological and left upper-limb ischaemic symptoms; it does not form a vascular ring. Treatment options include implantation of the subclavian artery to the aortic arch vessels and closure of the patent ductus arteriosus to prevent pulmonary run off. Here we describe a child who was incidentally detected to have this condition during evaluation of atrial septal defect for device closure.