A 7-year-old girl presented with an asymptomatic right supraclavicular swelling. Radiographs were interpreted as showing a non-union of her clavicle. No treatment was given at this time. However, she represented 12 years later with right upper limb pain and altered sensation. Examination revealed a positive Allen's test on the right. Repeat radiographs demonstrated a pseudarthrosis of the clavicle, associated with a secondary complication of thoracic outlet syndrome with vascular and neurological complications present. Non-operative management failed to relieve her symptoms. Operative intervention successfully treated her symptoms.