Introduction: Head and neck defects after tumor resection can be difficult to reconstruct using autogenous tissue without utilizing a free flap. Osteocutaneous fibula free flap is now considered the gold standard used for mandibular reconstruction after resections due to malignancy. Case presentation: We present the case of a 49-year old female known with an ectopic mucoepidermoid carcinoma involving the mandibula from one ramus to another. After tumor resection, we have reconstructed the mandible by using the only method available for reconstruction in this case - an osteocutaneous fibula free flap. We were able to reconstruct the mandible using 3D printed custom-made surgical guides. Discussion: Postoperative imaging showed that the height and symmetry of the mandible were satisfactory. There were no microvascular failures and the intraoral healing time was about 10 days. The donor site skin defect from the left leg was grafted with an autograft harvested from the ipsilateral thigh. The donor site healed uneventfully. Conclusion: Osteocutaneous fibula free flap is a highly effective method and sometimes the only one available for reconstruction of mandibular defects after resection of intraoral malignancies. Modern technologies, such as surgical planning using computer-aided design, play a critical part in extensive reconstructions, lowering the total intervention time.