Normalization of mandibular function in children is important for normal orofacial development because their function is not still matured. This case report examined jaw movement during chewing in a young patient with unilateral scissors-bite. He could hardly chew on the affected side, preferring to chew only on the unaffected side, and his minimum opening position was initially unstable, i.e., he had two positions before active treatment. Retention did not stabilize his minimal opening position and his dual-bite was not corrected. His minimal opening position was stabilized after equipping his upper canines with a resin cap. Although orthodontic treatment morphologically improved the patient's malocclusion, his function did not improve. Normal jaw movement on both sides was achieved after interfering with his old chewing pattern. Because normalization is needed for acquisition of normal function in children, long-term observations of their growth and functional changes are necessary after orthodontic treatment.