Free fibula is the workhorse flap for mandibular reconstruction and is increasingly being used in pediatric patients. However, craniomaxillofacial growth and development involve interdependent processes, and it remains unknown whether mandibular reconstruction with free fibula allows symmetric growth of the midface. The study evaluated midfacial symmetry after pediatric mandibular defect reconstruction. This retrospective cohort study included pediatric patients aged ≤14years who underwent mandibular reconstruction with free fibula flap. Postoperative computed tomography data were obtained at predefined follow-up time points. Midfacial symmetry was evaluated based on 3-dimensional (3D) cephalometry. The predictor variable was the side of the midface (affected or healthy side relative to the mandibular defect). The primary outcome variable was postoperative midfacial symmetry (at 1week, 6months, 1year, 2years, and >3years, or after the age of 18years), assessed in horizontal, vertical, and anteroposterior dimensions using 3D cephalometry. Another outcome variable was patient satisfaction based on a self-evaluation using visual analog scoring. Sex, age, diagnosis, and type of denture restoration. Paired t tests were performed to assess the relationship between the predictor and outcome variables, with the significance level of P<.05. A total of 13 patients were included in this study (9 males and 4 females; mean age: 12.23±2.39years). The average distance from upper first molar point (U6) to the horizontal plane on the affected side became greater than on the healthy side (difference: 0.7±0.5mm to 1.6±1.4mm, P<.05), while the average distance from pterygomaxillary fissure to coronal plane on affected side became shorter than that on the healthy side (difference: 0.6±0.6mm to 1.2±1.1mm, P<.05) from 1year after the surgery. There were no statistically significant differences in the remaining measurements between the 2 sides (P>.05). All the patients were satisfied with their postoperative facial symmetry. There were no severe midface deformities after pediatric mandibular reconstruction with free fibula flap. Meanwhile, pediatric mandibular reconstruction and proper occlusion could promote midfacial growth and symmetry.