Masticator space infection can easily be misdiagnosed as temporomandibular joint (TMJ) disorder. However, the association between masticator space infection and TMJ dislocation has not been studied. The present study describes a case of masticator space infection that initially presented as TMJ dislocation.A 63-year-old woman complained of dislocation and pain on the right TMJ for 3 weeks. Physical examination revealed right TMJ dislocation, which was confirmed by computed tomography (CT). Bimanual reduction of the dislocated TMJ was performed under general anesthesia with intermaxillary fixation. However, progressive right facial swelling was noted after the closed reduction of the right TMJ. Magnetic Resonance Imaging (MRI) revealed marked soft tissue swelling and mass forming-like change in the periarticular region of the right TMJ. Moreover, a necrotic area of the masseter and buccinator muscles was noted, which indicated dislocation-induced injury or hemorrhage. However, neoplasm arising from the joint space could not be ruled out. CT-guided biopsy was then performed, which showed chronic inflammation and necrotic tissue in the right masticator space, thus excluding the possibility of neoplasm. Extraoral Incision and Drainage (I&D) was then performed, and the final pathologic diagnosis coincident with cellulitis involved the masticator space and parotid spaces. After I&D and surgical debridement, the patient recovered satisfactorily.Although rare, we must consider the possibility of deep space infection when diagnosing patients presenting TMJ dislocation for their adequate and prompt management.