Desmoplastic fibroma (DF) is a rare benign bone tumor adopting an aggressive behavior, representing a challenge for clinical and radiographic diagnosis. This case report focused on a 31-year-old man with a large mandibular lesion with severe displacements of the mandibular teeth. Only a combination of paraclinical findings allows a definitive diagnosis to be made. Cervicofacial MRI revealed a low T1 signal intensity with peripheral enhancement after Gadolinium, and T2 hyperintense signal, while PET scan showed a moderate metabolism. Bone biopsy with immunohistochemical analysis allowed for definitive diagnosis of DF after eliminating the main differential diagnosis (fibrous dysplasia, fibrosarcoma, desmoid tumor, and osteosarcoma). The patient was successfully treated by large mandibular resection and reconstruction with a free-fibular bone flap”.