A patient with traumatic brain injury showed incomplete oculomotor nerve palsy in the subarachnoid space. A 12-year-old girl was hospitalized after a head injury. Neuro-ophthalmic examination showed that the left eye had a ptosis and pupillary involvement. An MRI indicated an intracranial hematoma at the basilar portion of the left temple. The ptosis and pupillary involvement improved after elimination of the hematoma. The presentation patterns are best explained by topographic organization of the third nerve fiber within the subarachnoid space. This case suggests that the topographic organization of the third nerve should be considered in diagnosis of oculomotor nerve palsy.