OBJECTIVE Facial nerve palsy after sagittal split ramus osteotomy of the mandible (SSRO) is a rare, but serious, complication. The aim of the present study was to evaluate the incidence of this complication, the possible causative mechanisms, its subsequent management, and eventual outcomes. METHODS All patients who underwent SSRO of the mandible at the Craniofacial Center, Chang Gung Memorial Hospital, Taiwan, from 1981 to 2008 were included in the present study. The patients reported as having postoperative facial nerve paralysis were identified and reviewed. RESULTS A total of 3,105 patients had undergone bilateral SSRO (6,210 sagittal splits). Of these 3,105 patients, 6 were reported as having unilateral facial nerve palsy postoperatively, for an incidence of 0.1%. One case was diagnosed as Bell's palsy. None of the patients with postoperative facial nerve palsy required surgical intervention, but all received physical therapy and medications. Complete recovery was obtained without sequela in all but 1 patient, who had incomplete frontal branch recovery. CONCLUSIONS Most facial nerve palsies that occur after SSRO of the mandible result from neurapraxia or axonotmesis, possibly from nerve compression or traction. Complete recovery can be expected in most cases, and conservative management without surgical exploration is recommended.