Since the inception of pancreas transplant as a treatment for type 1 diabetes mellitus, there has been considerable debate about the best way to manage exocrine secretions and monitor patients for graft rejection. For patients who undergo bladder exocrine drainage of a pancreatic allograft, a bladder-to-enteric drainage conversion can serve as a rescue procedure in case of anastomotic leaks or other complications. However, this procedure is associated with its own complications, including a rarely described enterovesical fistula. Here we report on a 45-year-old man who underwent a simultaneous kidney and pancreas transplant with bladder drainage to the latter. He developed a pancreatic allograft duodenal leak (duodenal-vesical anastomosis) requiring a bladder-to-enteric drainage conversion. The patient returned 2 weeks after discharge with an enterovesical fistula. He was treated nonsurgically with intravenous antibiotics, bowel rest, and parenteral nutrition, and the fistula successfully closed in approximately 2 weeks. Overall, enterovesical fistula formation is a rare but treatable complication that can occur after a bladder-to-enteric drainage conversion of a pancreatic transplant allograft. It can be managed nonsurgically, which is preferable in these immunocompromised patients.