Atezolizumab is a promising immunotherapy for advanced urothelial carcinoma. Like other immune checkpoint inhibitors, it can produce rare immune-related adverse events (IRAEs). Here we present the recent case of a patient with metastatic bladder cancer who developed diarrhea and abdominal pain months after beginning atezolizumab therapy. He presented to our institution with an ileal perforation secondary to atezolizumab-induced enterocolitis. After surgical repair, the patient's condition improved, and he was discharged. We discuss the management of atezolizumab-induced enterocolitis, including the importance of early recognition and intervention to prevent more devastating complications.