A 7-yr-old boy visited our surgical center with Pfeiffer syndrome type 1, presenting with macrocrania, broad big toe and thumb, exophthalmos, tongue protrusion, malocclusion with midfacial retrusion, mild respiratory difficulty due to minor upper airway obstruction, and developmental delay. He also exhibited anthrophobia with a passive character. The patient was treated with internal monoblock distraction osteogenesis to increase the intracranial and intraorbital volumes, and the nasal and pharyngeal airway spaces using two modular mid-facial internal distractors. For distraction, the latency period was 1 week, the daily activation of 1.0 mm was 20 days (total advancement 20 mm at the midline), and the consolidation period was 3 months. The follow-up computed tomography 12 months after surgery showed expansion of the brain and proper ossification in the distracted area. The patient also showed aesthetically good cranial contours, improved tongue and eyeball protrusion, no respiratory difficulty, and improved learning. We suggest that the internal distraction may last longer than an external type, resulting in a better bone fusion rate and successful expansion of craniofacial bones.