Central mucoepidermoid carcinoma is an uncommon tumor, accounting for 2% to 3% of all mucoepidermoid carcinomas. Meanwhile, a head and neck tumor rarely causes an attack of syncope. We describe a case of syncope considered to be caused by a large central mucoepidermoid carcinoma in the mandible. A 66-year-old man was referred to our clinic to receive treatment for a right mandibular lesion and to determine the cause of repeated attacks of syncope. Computed tomography showed that the right side of the mandible was remarkably expanded, and the parapharyngeal space was compressed by an expanded right mandibular tumor. Tumor biopsy was performed, and a mucoepidermoid carcinoma of the mandible was definitively diagnosed. No evidence of metastasis was evident on positron emission tomography. With the patient under general anesthesia, we performed a right hemimandibulectomy, right neck dissection, and immediate reconstruction using a pectoralis major myocutaneous flap and a reconstruction plate with condyle. We found no evidence of local recurrence or regional and distant metastasis at the 4-year postoperative follow-up. In addition, no attack of syncope occurred after the operation.