Tumor necrosis factor -alpha is an important cytokine that plays a role in inflammation and immune reactions. Tumor necrosis factor-alpha and its receptors are known to play a role in the pathogenesis of numerous immune-mediated diseases such as rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and inflammatory bowel disease. It is known that anti-tumor necrosis factor agents used in inflammation suppression and remission could lead to a series of para-doxical side effects. In this paper, we presented a case with ankylosing spondylitis in whom Crohn’s disease developed during etanercept treatment. A significant improvement was achieved in the symptoms and laboratory values by stopping etanercept treatment and switching to adalimumab.