Bony exostoses can occur at the site of a fracture but are rare in facial bones. We report a case of lateral rectus restriction secondary to a traumatic exostosis in the lateral orbital wall with resolution of diplopia after surgical removal of the lesion. Although orbital masses may cause extraocular muscle restriction, to our knowledge, restriction secondary to an exostosis has not been previously reported. A bony exostosis should therefore be included in the differential diagnosis of mechanical restriction of extraocular muscle movement, and surgical treatment is recommended in symptomatic patients.