The mandible is an important structure that is located in the lower third of the face. Large mandibular defects after tumor resection cause loss of its function. This study assessed the outcomes and tumor recurrence after immediate mandibular reconstruction using a free fibula osteocutaneous flap following radical resection of ameloblastoma.This is a retrospective non-randomized study of outcomes and tumor recurrence of all patients diagnosed with mandibular ameloblastoma from August 1997 until August 2017 (20 years) requiring free fibula osteocutaneous flap reconstruction at a single institution. The patients were identified through an electronic operative database; subsequently, their medical records and photo documentation were retrieved.Twenty-seven patients were included in this study. Eighteen patients were male, while nine were female. The majority of the patients (48.1%) were in their third decade of life when they were diagnosed with ameloblastoma. All of them underwent radical resection of the tumor with a surgical margin of 2 cm (hemimandibulectomy in cases with a large tumor) and immediate mandibular reconstruction with a free fibula osteocutaneous flap. Two patients required revision of a vascular anastomosis due to venous thrombosis postoperatively, while one patient developed a flap recipient site infection. The flap success rate was 100%. There was no tumor recurrence during a mean follow-up period of 5.6 years.Mandibular ameloblastoma should be treated with segmental mandibulectomy (with a surgical margin of 2 cm) to reduce the risk of recurrence. Subsequent mandibular and adjacent soft tissue defects should be reconstructed immediately with a free fibula osteocutaneous flap.