We experienced a case of delayed-onset Wallenberg's syndrome following cervical spine fracture coexisting with suspected conversion disorder. A 69-year-old man was involved in a traffic accident, and was admitted to our rehabilitation unit for the purpose of posttraumatic rehabilitation. At first, he complained of right occipital and nuchal pain. But his complaints changed to ataxia, dysphagia and a suspected brainstem lesion four months after the accident. His brainstem MRI showed a small ischemic lesion in the right dorsolateral area of the medulla oblongata. The long time lag between the original traumatic event and his changing complaints made the diagnosis difficult. Accordingly, rehabilitation assessment and conventional rehabilitation approaches were prepared for all of his symptoms. The dysphagia and ataxia were gradually reduced and the hemiparesis lessened and disappeared. A couple of points were suggested by this case. The first is “We must never overlook a change of neurological symptom masked as conversion disorder, and never deny what the patient says without careful listening.” The second is “We should offer the patient a conventional rehabilitation program without the option for malingering and falsification. This case might suggest that our attitude toward so-called gray-zone cases has an influence on the functional/social prognosis.