A 43-year-old male with a congenital absence of his left T1 rib developed a left-sided T1-T2 spinal facet joint arthrosis and stenosis and clinical signs and symptoms of T1 radiculopathy. The patient was treated with a decompressive laminotomy and partial medial facetectomy resulting in immediate resolution of symptoms. This report should alert clinicians to consider this potential etiology when evaluating patients with thoracic radiculopathy.