Osteoradionecrosis (ORN) is one of the most serious complications of oral and nasopharyngeal malignant neoplasms after radiotherapy. The incidence of mandibular ORN is significantly higher than that of maxilla. A radical surgical intervention such as mandibulectomy for advanced ORN is appropriate and effective to relieve pain and control infection. However, recovery of functionality and aesthetics is usually not the primary purpose of the one-stage radical surgery. Some patients often need a 2-stage operation owing to the bone defect, scar contracture, or recurrence. Although free flap has been proven as a reliable way to repair the complex maxillofacial defects, it is still a great challenge for surgeons to reconstruct the secondary complex mandibular ORN defects. Here, we report a case of secondary composite mandibular ORN reconstruction using the preoperative 3-dimensional biomodel planning and flowthrough radial forearm flap for free fibula osteocutaneous flap.