This article reports a rare case of a temporomandibular joint (TMJ) chondrosarcoma in a child. Chondrosarcoma is a malignant cartilaginous neoplasm that resembles synovial chondromatosis. In the head and neck region, chondrosarcoma is uncommon, corresponding to 6.4% to 12% of all reported cases. The majority of patients with chondrosarcoma are in the third to fourth decades of life. A Pubmed search showed that 20 TMJ chondrosarcoma cases had been reported up to 2008. The present case was of an 11- year-old girl referred to an Oral Disease Center and presenting with a preauricular swelling on the right side and normal ENT evaluation. The patient was healthy. Discrete pain and mild limitation of mouth opening were observed. A panoramic radiograph as well as computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI) revealed an osteolytic lesion in the right TMJ. The skull base and adjacent spaces were preserved but adjacent anatomic structures were displaced. After an incisional biopsy, the patient underwent high condylectomy. Microscopic findings showed a tumor exhibiting cartilaginous tissue proliferation with celullar pleomorphism, nuclear hyperchromasia, and mixoid changes in the matrix. The immunohistochemical analysis of the expression of Ki-67 and Cyclin B1 proteins (cellular proliferation markers) revealed a very low proliferative cell index. The 3.5 years of clinical and imaging follow-up have shown no evidence of recurrence or metastasis, but signs of myofascial disorders could be observed. It is concluded that cartilaginous lesions in the jaws must be regarded with suspicion, since benign and malignant lesions may show similar clinical features. This case emphasized the importance of interdisciplinary approaches to minimize the possibility of misdiagnosis. Parole chiave: chondrosarcoma, malignant neoplasm, synovial, temporomandibular joint