Posttransplant anemia is a common problem that may hinder patients' quality of life. It occurs in 12 to 76% of patients, and is most common in the immediate posttransplant period. A variety of factors have been identified that increase the risk of posttransplant anemia, of which the level of renal function is most important. Sirolimus, a mammalian target of rapamycin inhibitor, has been implicated as playing a special role in posttransplant anemia. This review considers anemia associated with sirolimus, including its presentation, mechanisms, and management.