INTRODUCTION The increased incidence and success of strip craniectomy with postoperative helmet therapy in the treatment of sagittal craniosynostosis has been documented by multiple centers throughout the country and world. The authors report a child with a postoperative implantation intradiploic epidermoid cyst following a strip craniectomy, a complication, that to our knowledge, has not been reported. METHODS This clinical report involves a 3-year-old boy with a scaphocephalic appearance who was transferred to our center following an interstate adoption. He underwent a strip craniectomy with helmet therapy in infancy. On presentation to our facility the chief complaint was a scaphocephalic appearance. Preop computed tomography scans showed areas of bone gaps along the sagittal suture. RESULTS The child was brought to the operating room for a mid-vault expansion. At surgery, a large intradiploic epidermoid cyst was noted on the posterior aspect of the area of the sagittal suture, immediately beneath to posterior incision for the strip craniectomy. The cyst extended through the inner table of the skull and necessitated split cranial grafts to aid in the reconstruction. CONCLUSION The authors present a patient with an iatrogenic intradiploic epidermoid cyst of the posterior skull following strip craniectomy, which has not been previously been described in association with strip craniectomy. This patient underlies the importance of a strong working relationship between craniofacial surgery and neurosurgery.