Nivolumab is a fully human immunoglobulin G4 immune checkpoint inhibitor antibody approved for use in the treatment of several malignancies such as lung cancer. Cutaneous reactions to checkpoint inhibitors are frequent, appearing in approximately 40% of patients. Although most of the reactions are well tolerated, these drugs can lead to severe cutaneous adverse reactions, but a quick recognition of the symptoms can significantly decrease their mortality. In this case report, we describe a patient with metastatic squamous lung cell carcinoma suffering from nivolumab-induced Stevens-Johnson syndrome with severe skin denudation and mucosal involvement.