Immune checkpoint inhibitors (ICIs) have been increasingly used in the treatment of several malignancies and may target cytotoxic T-lymphocyte-associated antigen-4, programmed cell death-1, and programmed cell death ligand 1, which work on maintaining peripheral immune tolerance. ICIs inhibit these ligands causing an immune-enhancing effect, leading to a wide spectrum of complications from mild mucositis to life-threatening pneumonitis or hepatitis. These complications are collectively called immune-related adverse events. Their prevalence has increased with a rise in ICI use, with rare manifestations being reported in popular literature. We present a case of hemorrhagic gastritis due to the anti-programmed cell death-1 antibody, pembrolizumab.