This brief overview discusses the beneficial and deleterious effects of mTOR inhibitors on beta-cells, and how sirolimus- and everolimus-based immunosuppression have impacted on practices and outcomes of pancreas and islet transplantation. Sirolimus was the cornerstone of immunosuppressive regimens in islet transplantation at the turn of the millenium, but utilization of mTOR inhibitors has progressively decreased from >80% to <50% of islet transplant recipients in more recent years. For whole pancreas transplantation, mTOR inhibitors were used in approximately 20% of patients in the early 2000s, but this dropped over the years to <10% currently. This decrease is arguably due to less well tolerated side effects without the advantage of better outcomes. Nonetheless, mTOR inhibitors remain extremely valuable as second line immunosuppressants in pancreas and islet transplantation.