We present a rare case of dermatomyositis associated with nivolumab therapy for melanoma. Nivolumab is an immune checkpoint inhibitor that blocks the programmed death-1 (PD1) receptor and has a number of associated immunotherapy related adverse events. Although most are T-cell mediated, some are antibody mediated mimics of classical autoimmune diseases. We review the characteristics of other cases of anti-PD1 associated dermatomyositis and the recent literature to better understand how to classify and treat this challenging immunotherapy related adverse event.