Immune checkpoint inhibitors, such as ipilimumab (an anti-CTLA4 antibody), have become a commonly used therapy in cancer. To date, safety data of patients with underlying autoimmune disease is limited. We present a case of a patient with rheumatoid arthritis who was diagnosed of a BRAF-mutant metastatic melanoma. The patient was treated with ipilimumab and presented with high-grade colitis requiring immunosuppressors. Despite of the immune-related adverse event, no exacerbation of the rheumatoid arthritis was observed and the patient achieved a complete response. This case report contributes to the scarce literature on the use of immune checkpoint inhibitors in patients with an underlying autoimmune condition.