Enormous oromandibular defects in children remain a reconstructive challenge due to the region's unique features and the scarcity of a perfectly matched recipient site. The osteocutaneous fibula-free flap (OCFFF) is an excellent option for these defects. Most reports on oromandibular reconstruction in children are limited to surgical techniques instead of long-term follow-up, especially in resource-limited settings. We reported a 9-year-old child who presented with a massive oromandibular defect caused by a high-energy gunshot. Firstly, the patient was treated with debridement, lower defect edges approximation, and tracheostomy. After one week, the procedure of OCFFF was performed, and two months later, the lower lip was reconstructed using a tongue flap. The aesthetic outcome was excellent at two years, and the patient could speak and eat without impaired oral function. In conclusion, microsurgical reconstruction using OCFFF for massive oromandibular defects in our child patient was safe with satisfactory facial aesthetics and oral function.