Skeletal Class III malocclusion with mandibular prognathism is often associated with mandibular asymmetry, and patients with Cl III deformity and asymmetry may undergo orthognathic surgery to improve facial function and esthetics. However, the long-term stability of mandibular setback surgery has been considered "problematic". We report a 25-year-old female patient who was diagnosed as having a skeletal Class III relationship, mandibular asymmetry and unilateral crossbite. She underwent bilateral sagittal split-ramus osteotomy and orthodontic therapy, and this led to improvement of her dentofacial relationship, esthetics and occlusion. The outcome was stable after 8 years of retention. This case shows that asymmetry correction using mandibular setback surgery for skeletal Class III deformity can yield long-term stability.