The nasopharynx is located in the mid-facial portion and is difficult to access in surgery. In the trans-cervical approach, surgery is performed from the submandibular region through the parapharyngeal space. However, no report has explained the procedure in detail, especially when the mandibular bone is preserved. In this report, a case of T3 oropharyngeal posterior wall cancer extending into the nasopharynx is presented with a detailed description of the surgical procedure. In the operation, dissection proceeded from the submandibular region along the styloid diaphragm and the fascia covering the medial pterygoid muscle. The muscles associated with the styloid process （stylohyoid, styloglossus and stylopharyngeus muscles）, ones with auditory tube （levator veli palatine, tensor veli palatine） and the pharyngobasilar fascia were sequentially identified. After the lateral wall of the pharynx was widely exposed, the tumor was resected en bloc. The mucosal defect was reconstructed with free jejunal flap. The laryngeal framework was removed and subglottic mucosal closure was performed to maintain oral intake. The postoperative course was uneventful except for facial palsy which resolved without intervention. The trans-cervical approach to the nasopharyngeal space can be performed in systematic fashion and is a useful method for resecting oropharyngeal cancer extending into the nasopharynx.