BSSRO (bilateral sagittal split ramus osteotomy) is an effective surgical method for maxillofacial deformities. Rigid fixation using a plate and screws can stabilize bony segments and induce early mouth opening. Though this procedure has a low complication rate, normal function and esthetic recovery is achieved through proper and early management of the complications. Complications consisting of temporomandibular disorders, sensory disturbances due to inferior alveolar nerve damage, open bite, malunion or nonunion, and facial nerve palsy occur, but these rarely develop. Facial nerve palsy causes the muscles involved in facial expression to depress, which results in ocular dryness or retinal damage. When facial nerve palsy develops, early management involving steroid medication and physical therapy is effective. In the case of severe damage, surgical intervention should be considered. A 20-year-male patient came to the oral and maxillofacial surgery department for orthognathic surgery. The mandible was set back by BSSRO under general anesthesia. Facial nerve palsy was observed on the left side of the face: steroid and vitamins were administered early and physical therapy was performed daily. These forms of management can aid in function and allow for gradual esthetic recovery. Presumed causes were excessive soft tissue retraction or soft tissue injury by the osteotome at the horizontal osteotomy of the ramus. Careful dissection, retraction and a precise osteotomy are needed for protection of the facial nerve. If nerve damage is observed, early management can help in the recovery of facial nerve function and esthetics.