A patient with thyroid-associated ophthalmopathy was treated with teprotumumab and developed symptoms concerning for inflammatory bowel disease after her sixth infusion. Colonoscopy was performed, and mucosal biopsies identified evidence of active colitis consistent with a diagnosis of ulcerative colitis. Despite treatment with budesonide and mesalamine, the patient continued to be symptomatic one and a half months after cessation of teprotumumab and required infliximab to achieve good control of her inflammatory bowel disease. This case represents the first report of new-onset inflammatory bowel disease arising during treatment with teprotumumab.