A 77-year-old patient treated with ipilimumab (anti-CTLA-4 antibody) for metastatic melanoma developed autoimmune pancytopenia (anemia, thrombocytopenia, and neutropenia) 8 days after the fourth infusion. This pancytopenia was resistant to high-dose oral corticosteroids (1 mg/kg) and to hematopoietic growth factors. It resolved after intravenous immunoglobulins injection. To date, only 1 case of autoimmune pancytopenia has been reported after this treatment. According to the case that we report, it seems essential to control the leukocyte count before any injection of ipilimumab.