Immunotherapy has nowadays become part of the mainstay of treatment for several cancers. In this report, we present a case of toxic epidermal necrolysis (TEN) occurring as a relatively rare complication of pembrolizumab, which is a humanized monoclonal anti-programmed cell death-1 (anti-PD1) IgG4 antibody that targets tumours expressing PDL-1. In our case, this monoclonal antibody (MAB) was being used for the treatment of metastatic non-small cell lung cancer, before being withheld because of this potentially life-threatening reaction. There are no guidelines on the optimal management of TEN, with varying reports on the efficacy on steroids, intravenous immunoglobulin (IVIG), and cyclosporin. In this report, we describe a case of TEN following the second dose of three-weekly pembrolizumab in a 50-year-old man, comparing it to four similar cases reported in the literature. It is important that oncologists are aware of this potentially life-threatening adverse reaction of pembrolizumab, as early recognition and treatment of TEN are essential to improve clinical outcome.