The technique of distraction has revolutionized the treatment of mandibular hypoplasia; however, presently large mandibular defects still require bone grafts. Microvascular grafting is commonly used in adults. Conversely, in pediatric reconstruction, nonvascularized rib grafts remain standard. Unfortunately, resorption of nonvascularized bone remains a major issue, particularly when soft tissue is hypoplastic. This case study represents a combination of techniques in the treatment of severe mandibular deficiency, and introduces the concept of distraction mesenchymogenesis. The patient was a 2½-year-old boy with severe bilateral Pruzansky class III mandibular hypoplasia. He had a permanent open mouth posture, an overjet of 23 mm, and was unable to move the lower mandibular segment. His oropharyngeal airway diameter was 2.2 mm and he was tracheostomy dependent. The patient was treated with distraction of the lower jaw mesenchyme followed by bilateral functional free fibular microvascular flaps containing reinnervated muscle. This created a well-vascularized body, ramus, and condyle bilaterally within an adequate soft-tissue envelope. Postoperatively, the overjet was reduced to 5 mm. The patient can now actively move his mandible. Airway diameter increased to 10 mm, and the patient is able to tolerate intermittent tracheostomy plugging. This innovative combination of techniques allows early intervention, limits graft resorption, and improves airway control.