Introduction: Ameloblastic carcinoma is an extremely rare malignant odontogenic tumor with predominantly mandibular localization. In most cases, it is treated surgically. Observation: Here, we describe a case of ameloblastic carcinoma. The patient presented a large expansive mass on the ascending branch of the left mandible, which was ulcerated and communicating with the oral cavity. He refused the proposed surgical treatment after being informed of the risk of facial decomposition. After several years, due to progressive symptomatology, he received palliative radiotherapy of 60 Gy divided into 30 sessions. Local control of the disease was achieved. Discussion: The efficiency of radiotherapy for ameloblastic carcinoma remains controversial. Conclusion: Radiotherapy appears to be a second-line approach when surgery is not feasible for ameloblastic carcinoma treatment.