Hypomagnesemia is considered as an independent risk factor for new-onset diabetes mellitus after kidney transplant. New-onset diabetes mellitus is an important comorbidity associated with allograft failure. In this study, our aim was to investigate the correlation between hypomagnesemia and preva-lence of posttransplant diabetes mellitus. We retrospectively evaluated 189 pediatric renal transplant recipients who underwent their first renal transplant. A patient with type 1 diabetes mellitus before transplant was excluded from the analysis. Hypomagnesemia was defined as having serum magnesium levels lower than 1.7 mg/dL. Diabetes was defined according to American Diabetes Association criteria. Serum magnesium and glucose levels at month 1 after transplant were recorded. We evaluated the records of 188 patients. New-onset diabetes mellitus was diagnosed in 7 patients (3.7%). Hypomagnesemia was shown in 50% of patients (64/120). Mean glucose levels were higher in those with hypomagnesemia than in patients without hypomagnesemia (119.2 vs 91.56 mg/dL, respectively; P = .01) A significant negative correlation was observed between serum magnesium and glucose levels (r = -0.53; P < .05). Mean serum magnesium level in patients with new-onset diabetes mellitus was lower than in patients without diabetes (1.56 ± 0.21 vs 1.75 ± 0.26 mg/dL; P = .052). Hypomagnesemia is a common problem in pediatric renal transplant. The relationship between serum magnesium and glucose levels suggests that hypomagnesemia plays a role in the development of new-onset diabetes mellitus after transplant. Compre-hensive studies are needed to support this association.