Mandibular asymmetry is among the most common facial anomalies. Traditionally, mandibular asymmetry with malocclusion has been treated with orthognathic surgery and genioplasty. However, routine genioplasty cannot achieve a satisfactory contour. Hence, this study presents a modified technique, himi-lengthening genioplasty, to resolve this matter. By combining this technique with orthognathic surgery, the authors successfully corrected mandibular asymmetry in 1-stage surgery, achieved ideal occlusion, and reconstructed the esthetic contour. No complications occurred during the 6-month follow-up period. Therefore, the authors recommend our modified surgical technique for its effectiveness, security, stability, and simplicity.