A 15-year-old boy was diagnosed as having Wilson disease. He perceived involuntary tongue movement and speech disorder since March 1990. The tongue movements presented in the resting state and during action. It contracted transversely and bilaterally with an irregular frequency about 1 Hz. As a result, the sides of the tongue moved to form a narrow central groove. This was quite different from the tongue protrusion of tardive dyskinesia. His speech had imprecise consonants, monopitch, low pitch, low volume, harsh voice, and hyponasality. These suggested that tongue dyskinesia could be an early sign of Wilson disease and was not the main cause of his dysarthria.