Transformation of an ameloblastic fibroma to an ameloblastic fibrosarcoma has been reported rarely in the literature. The present case report describes such evolution in a patient under long-term follow-up. The patient was first treated in 2008, and he developed the malignant counterpart of the disease 2 years later. The patient is currently under careful long-term follow-up and is free of disease. This article describes the clinical and radiographic features, histological characteristics, immunohistochemical findings, and surgical treatment of the tumor.