Introduction: The combination of non-vascularized iliac crest bone graft and distraction osteogenesis in a second surgical intervention has only been described to achieve alveolar ridge augmentation. This technique is not recommended to treat bone defects of the jaws caused by firearm projectile. Case presentation: 40-year-old woman with a segmental mandibular defect in the mandible body caused by the impact of a firearm projectile at the age of 1 year. The patient developed a severe Class II dentofacial anomaly that required a two-stage treatment; she underwent mandibular reconstruction with free iliac crest bone graft followed by a bilateral mandibular distraction at the level of the iliac crest bone graft. With these interventions, a remarkable improvement of the patient's malformation was achieved. Conclusion: Horizontal distraction of the free iliac crest bone graft is a safe and predictable procedure to treat dentolabial anomalies requiring mandibular reconstruction. This procedure was performed in the patient without complications. Further studies on the effectiveness of this technique are required.