An osteochondroma is rare in the facial skeleton because of the intramembranous origin. This paper describes an uncommon case of osteochondroma of mandibular condyle with secondary synovial chondromatosis in a 43-year-old woman, who had an occlusal splint and orthodontic treatment without an accurate diagnosis for more than two years. The patient visited Chonbuk National University Hospital with the chief complaint of facial asymmetry and difficulty in chewing food by malocclusion. Cone-beam computed tomography revealed the presence of a radiopaque mass with loose bodies, which developed from the anterior portion of the right condylar neck and extended into the condylar head. The patient underwent tumor excision and condyloplasty subsequent to the clinical and radiographic diagnosis of osteochondroma with synovial chondromatosis. The histopathological diagnosis revealed osteochondroma, which consisted of proliferative bony and hyalinized cartilage tissues. The patient had been followed up for two years and there had been no evidence of recurrence.