Abstract :Psoriatic arthritis(PsA)is a chronic, disabling inflammatory disease, associated with psoriasis. Involvement of the Temporomandibular Joint (TMJ) is very rare and may cause severe deformation or dysfunction. In this article, the authors presented a case of fibrous Ankylosis of TMJ caused by PsA and its natural history after 4 months. The findings of the report suggested that PsA in TMJ may progress rapidly in an early age without any treatments. Further study for the development of the TMJ lesion caused by PsA is quite necessary.