Iridocyclitis is an inflammatory lesion of the eye that is related to ankylosing spondylitis and can be one of the symptoms of ankylosing spondylitis. Iridocyclitis can be caused by a number of factors, including pathogenic infections, autoimmune factors, and trauma, and is primarily characterized by eye pain, photophobia, and blurred vision. When problems with the autoimmune system lead to iridocyclitis, it is often prone to complications such as rheumatoid arthritis and ankylosing spondylitis. Iridocyclitis is a common extra-articular symptom of ankylosing spondylitis, and some early cases of ankylosing spondylitis do not show the typical sacroiliac joint pain, but only iridocyclitis. When ankylosing spondylitis is complicated by iridocyclitis, nonsteroidal anti-inflammatory drugs should be administered along with ophthalmologic therapy, and when this is not effective, biologic agents should be considered. Therefore, when iridocyclitis is present, especially in young men, one should be alert to the possibility of ankylosing spondylitis. When ankylosing spondylitis is diagnosed, it is also important to check for iridocyclitis so that a timely diagnosis can be made and treatment can be targeted.