Cranial distraction osteogenesis has been applied as a mode of therapy to patients with various types of craniosynostosis. Several minor complications during distraction have been reported in the previous literature, including infection, device exposure, and dislocation and distortion of the device. To our knowledge, this is the first report of 2 cases of spontaneous device breakage during cranial distraction osteogenesis. Two infant patients were diagnosed with shunt-induced microcephalies. The ages of the 2 patients were 8 and 12 months. Their head circumferences were 3 percentiles below that of normal children of the same age. Distraction osteogenesis advancement to the frontal skull and the orbital bar was performed with two distractors. We distracted a total of 7.0 and 14.4 mm at a rate of 0.6-1.5 mm per day before device breakage occurred 7 and 25 days after the distraction activation, respectively. Both patients underwent reoperation to exchange the broken device for further distraction. To prevent further device breakage, we suggest increasing the rate of distraction, placing stronger or more devices, or relieving the scalp retraction pressure probably by extensive dissection of the subcutaneous layers or multiple incisions into the galeal layers.