Crohn’s disease is a chronic, or long lasting inflammatory disease in the gastrointestinal (GI) tract. Most commonly, Crohn’s disease affects the small intestine and the beginning of the large intestine. Treatment for Crohn’s disease usually involves drug therapy or, in certain cases, surgery. Several side effects develop from the use of drugs. A case with Crohn’s disease refractory to 5-ASA, corticosteroid and azathioprine treatments who developed breast carcinoma following infliximab treatment is being presented in this report. Case: SE, aged 44 years, presented to our polyclinic with weight loss, abdominal pain and flatulence. The patient had no response to mesalazine, steroid and azathioprine therapy. Upon identifying inflammatory stricture with abdominal MR, the medicines the patient has been using was discontinued and anti-TNF alpha (infliximab) treatment was initiated after receiving the consent of the patient. At 3rd month of treatment, the patient detected a small mass at the left breast. Mastectomy was performed and axillary lymph nodes were resected. Because breast cancer was detected following infliximab treatment in this case, we believe that a breast examination (physical examination, mammary USG) must be performed in female patients prior to infliximab therapy.