We present the case of a 47-year-old male with a personal history of radically removed malignant melanoma (pT3bN2M0) who was receiving adjuvant nivolumab for the prevention of recurrence. He was admitted to our service complaining of epigastric pain and hyporexia after receiving the ninth dose of nivolumab. He underwent a preferential esophagogastroduodenoscopy, which showed intense inflammation limited to the stomach.