Purpose Head trauma can lead to aberrant regeneration of the third cranial nerve (oculomotor nerve). Background Aberrant regeneration of the third cranial nerve is most commonly due to its damage by trauma. Case report We report here the case of a patient who, following severe head injury, suffered from diplopia, abnormal deviation of the right eye (exotropia, moderate limitation in elevation and adduction), and overaction of the left lateral rectus. Neither ptosis nor limitation of sursumduction was seen in the right eye. Surgery was carried out for relieving diplopia due to aberrant regeneration of the third cranial nerve affecting the right eye. Right medial rectus resection (7 mm) and left lateral rectus recession (9 mm) were performed. Diplopia disappeared in the sixth week after operation. Conclusion Traumatic third nerve palsy may result in aberrant regeneration of the third cranial nerve. The full-blown features of this syndrome may or may not be present. Diplopia was relieved by performing surgery in both the affected eye (right medial rectus resection) and the healthy eye (left lateral rectus muscle recession).