Thoracic Outlet Syndrome (TOS) describes a variety of symptoms caused by the compression of the neurovascular structures in the cervicoaxillary region as they leave the thorax toward the upper limbs. Causes of TOS are vascular and neurogenic, with neurogenic symptoms being the most common presentation (95% of patients). Symptoms related to neurogenic TOS include intrinsic hand muscle and thenar region atrophy and weakness, as well as medial hand and forearm numbness, which are all suggestive of lower trunk involvement. This condition is very rare in the pediatric population. We are reporting a case of true neurogenic TOS caused by a fibrotendinous band in an adolescent with bilateral cervical ribs who was submitted for surgical treatment at the right side.