Facial nerve palsy following a sagittal split ramus osteotomy is a rare but serious complication. Its incidence reported to vary from 0.17% to 0.75%. Many factors may contribute to this complication; these include damage from retraction, fracture of the styloid process, excessive distal movement of the proximal mandibular segment, and postoperative edema. The case of a 20-year-old man who underwent sagittal split ramus setback osteotomy is described. He experienced Rt. facial nerve palsy immediately after his surgery. However, after facial nerve decompression OP, he almost regained normal function within 3 months. So, we report a case ; postoperative facial nerve palsy.