A case of squamous cell carcinoma of the tongue with advanced N3 cervical lymph node metastases in an 80-year-old female is reported. The patient was treated with a combination of radiotherapy (2 Gy/day, total 60 Gy), superselective intra-arterial chemotherapy via a superficial temporal artery and a femoral artery (docetaxel, total 124 mg; cisplatin, total 135 mg), and four sessions of hyperthermia for cervical lymph node metastases. The tumor responded well to therapy, and 18-fluorodeoxyglucose uptake in both primary and neck lesions disappeared on positron emission tomography-computed tomography. The patient has shown no clinical or radiological evidence of local recurrence or distant metastases 6 years after the end of treatment. Advanced oral cancer patients with N3 cervical lymph node metastases are particularly difficult to treat and have a poor prognosis. This method of thermochemoradiotherapy seems a promising modality for patients with N3 cervical lymph node metastases of oral cancer.