Purpose: Traditionally, less rigid fixation techniques have been applied to the pediatric cervical spine. There is a lack of long-term outcome data for rigid fixation techniques. The purpose of this study was to define the clinical outcome and safety of posterior instrumented fusion in the pediatric population using adult posterior instrumentation.Methods: A multicenter, retrospective review of pediatric patients who underwent posterior cervical fusion using a 3.5 mm posterior cervical system for any indication was performed. Outcome parameters included complications, revision and fusion rates, operative time (OR), blood loss, and postoperative neurologic status. Outcomes were compared between patient groups (posterior only versus anterior/posterior approach, short versus intermediate versus long fusion, and between different etiologies) using Mann–Whitney and chi-square test.Results: Seventy-nine patients with a mean age of 9.9 years and mean follow-up of 2.8 years were included. At baseline 44 (56%) had an abnormal neurologic exam. Congenital deformities and basilar invagination were the most common indications for surgery. Posterior-only surgery was performed in 71 (90%) cases; mean number of levels fused was 4 (range 1–15). Overall, 4 (5%) operative complications and 4 (5%) revisions were reported at an average postoperative time of 2.6 years. Neurologic status remained unchanged in 74%, improved in 23%, and worsened in 3%. When comparing outcome measures between the various groups, 2 significant differences were found: OR was longer in the anterior/posterior approach group and decline of neuro status was more frequent in the long fusion group.Conclusion: Posterior cervical fusion with an adult 3.5 mm posterior cervical system was safe in this cohort of 79 pediatric patients irrespective of surgical technique, fusion length, and etiology, resulting in a high fusion and low complication/revision rate.