Trismus is a disturbing condition with varied etiology, one of them is Extra articular ankylosis. The extra articular ankylosis has been reported in the literature as a fusion of the coronoid process to the zygomatic bone or to the skull base. However, there are a very few cases reported in the literature that highlights a pathologic tumor of mandible leading to extra-articular ankylosis and subsequently resulting in trismus. We hereby present a unique case of young adult having restricted mouth opening due to the bony fusion of the mandibular ramus to the zygomatic bone and zygomaticomaxillary buttress region due to a pathologic tumor diagnosed as Ossifying Fibroma.