Aim: An odontogenic keratocyst (OKC) of the mandible is a benign intraosseus lesion of odontogenic origin characterized by a high recurrence rate. In this case report, we highlight the challenging diagnosis and propose a potential treatment for an extensive OKC with lingual expansion. Summary: A 26-year-old male with an OKC in the ramus of the right mandible near the second and third molars was treated by a combined intra/extra-oral approach. A reconstruction plate was adapted and fixed by extra-oral submandibular access, followed by intra/extra-orally executed enucleation. Key learning points: The combined intra/extra oral approach seems a reasonable technique for the treatment of similar extensive OKC's in order to avoid pathological fractures as well as guaranteeing total removal of the lesion.