An elongated styloid process (ESP) causes symptoms such as pharyngeal pain, swallowing pain, and discomfort during mouth opening. The main treatment is surgical resection of the ESP. The authors present a case of ESP with skeletal mandibular protrusion. Because mandibular setback by sagittal splitting ramus osteotomy (SSRO) may lead to deterioration of symptoms of ESP, resection of ESP and bilateral SSRO were performed simultaneously. The patient was a 50-year-old man who visited our department with chief complaints of mandibular protrusion and pain in the left pharynx on mouth opening and swallowing. A lateral cephalogram helped in diagnosis of skeletal mandibular protrusion. In addition, an approximately 42-mm left styloid process elongated inferomedially was observed. Left styloidectomy was first performed via the cervical approach, followed by SSRO. Occlusion, facial appearance, and preoperative symptoms due to the ESP improved after surgery. The cervical appearance was esthetically satisfactory. In a case of ESP with skeletal mandibular protrusion with potential aggravation of symptoms because of mandibular setback of the ESP, resection of the styloid process is necessary together with orthognathic surgery.