A 68-year-old male presented with progressive quadriparesis. Twelve years previously he had undergone anterior decompression with bone grafting for cervical ossification of the posterior longitudinal ligament associated with spinal trauma. Radiological examination showed ossification of the transverse ligament of the atlas (TLA) and severe stenosis of the upper cervical canal. Anterior dislocation of the atlas was also present, but the occiput/atlas/axis unit was perfectly stable due to the prior anterior fusion. Suboccipital decompression and laminectomy of the atlas were performed, and his symptoms improved. Based on the atlanto-axial dislocation, the TLA might have been damaged at the time of the primary trauma and became the trigger for the ossification of the TLA, showing that marked ossification of a vertebral ligament can occur after injury.