Von Recklinghausen's disease is a syndrome defined by the presence of café-au-lait spots and multiple benign neurofibromas. We report a 12-year-old boy with involvement of the tongue associated with von Recklinghausen's disease. The patient presented with a chief complaint of a mass of the tongue. Clinical examination showed multiple brown pigmented spots of the skin and a painless mass in the left side of the tongue. Clinical diagnosis was a tongue tumor associated with von Recklinghausen's disease, and the tumor was surgically excised. Histopathologically, the specimen was diagnosed as plexiform neurofibroma. No gene abnormality can be found by G-banded analysis and fluorescence in situ hybridization (FISH) analysis. The patient showed no evidence of recurrence during the next 1 year, but careful follow-up is needed because the malignant tumor associated with von Recklinghausen's disease might occur in the oral region.