To identify risk factors associated with the development of diabetes mellitus and to describe the prevalence of diabetes in pediatric hematopoietic cell transplant (HCT) survivors. The follow-up records of 748 patients who survived for at least 2 years after pediatric HCT were retrospectively reviewed for diagnosis of diabetes. Risk factors for type 2 diabetes were analyzed using multivariate statistics. Among 748 patients with a median of 11 years of follow-up, 38 developed diabetes after HCT. Four patients (three leukemia and one neuroblastoma) developed type 1 diabetes 8 to 14 years after HCT, at between 10 and 19 years of age. Thirty-four patients (32 leukemia and 2 aplastic anemia) developed type 2 diabetes 1 to 24 years after HCT, at between 11 and 41 years of age. Of the 34 patients with type 2 diabetes, 23 were non-Hispanic white, 3 had experienced asparaginase toxicity (hyperglycemia and/or pancreatitis), and 26 had a family history of diabetes. Risk factors associated with type 2 diabetes were diagnosis of acute or chronic leukemia, race/ethnicity other than non-Hispanic white, family history of diabetes, and asparaginase toxicity. The prevalence of type 1 diabetes among all surviving patients was 0.52%, or three times higher than the general U.S. population. The prevalence of type 2 diabetes was 9% among leukemia survivors and 2% among aplastic anemia survivors, both higher than expected. Pediatric HCT survivors are more likely to develop diabetes than the general population.