Behçet's disease (BD) is a systemic vasculitis, while myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematologic disorders characterized by ineffective hematopoiesis. Some studies suggest a relationship between MDS and BD, especially intestinal BD, and trisomy 8 seems to play an important role in both diseases. There are several reports on patients with BD comorbid with MDS involving trisomy 8 that frequently have intestinal lesions refractory to conventional medical therapies. Tumor necrosis factor (TNF)-α is strongly involved in the pathophysiology of several autoimmune diseases such as rheumatoid arthritis, inflammatory bowel disease, and BD. In addition, TNF-α plays an important role in the pathophysiology of MDS by inhibiting normal hematopoiesis and inducing the programmed cell death of normal total bone marrow cells and normal CD34+ cells. Recent clinical reports demonstrate the favorable effect of TNF-α antagonists in patients with refractory intestinal BD and in those with MDS. We present the case of a patient with intestinal BD and MDS involving trisomy 8 who was successfully treated with adalimumab.