A 73-year-old man presented with well-differentiated squamous cell carcinoma of the tongue (T3N0N0). After the completion of external beam radiotherapy (32 Gy) and oral tegafur-uracil (UFT) administration, the tumor had clinically disappeared. Two years later, a recurrent lesion was confirmed histologically. Without any specific therapy, the tumor gradually and spontaneously regressed, from 4 months after the recurrence was diagnosed, and it had completely disappeared both clinically and by computed tomography imaging at 1 year and 4 months after recurrence. There was no evidence suggesting regrowth of the disease in the patient at 3 years and 7 months after the histological confirmation of tumor recurrence.