Temporomandibular joint cysts usually occur between the second and fourth decade of life. There is a female predominance to male of approximately 3 to 1. The patients complain of swelling, pain and sometimes decreased mouth opening. Synovial cysts of the temporomandibular joint seem to develop by an increase of intraarticular pressure due to trauma or inflammation which causes capsular herniation. However, if inflammatory synovial cysts develop by an increase of synovial fluid into inflammation tissue in the capsule without capsular herniation, a differential diagnosis should include synovial chondromatosis and synovitis. This is a case report of a synovial cyst developed in a capsule of the temporomandibular joint.