BACKGROUND: Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. They pose challenges, particularly in the form of immune-related adverse events (irAEs). Although cases of gastrointestinal irAEs have been well-documented, acute esophageal necrosis (AEN) characterized by a circumferential blackening and fragility of the esophagus, weeks after immunotherapy discontinuation, has not been reported. CASE PRESENTATION: A 75-year-old diabetic male who was recently diagnosed with high-grade papillary urothelial cancer with liver and retroperitoneal metastases and had undergone radical cystectomy with ileal conduit urinary diversion, presented to the hospital for sepsis secondary to a urinary tract infection. While in the hospital, he experienced hematemesis, with an acute drop in hemoglobin from 10.6 to 5.3 g/L and a rise in serum lactate from 1.5 to 3.6 mmol/L. An esophagogastroduodenoscopy (EGD) revealed diffuse circumferential eschar, exudate, and inflammation. He was diagnosed with acute esophageal necrosis (AEN), which was found to be secondary to his pembrolizumab use. CONCLUSION: Immune-related adverse events will remain a challenge in patients receiving ICI therapy. AEN is a rare life-threatening irAE associated with ICIs. Further research is warranted to clarify the exact mechanism of injury, optimal treatment strategies, and possible preventative measures.