Despite accumulating evidence suggesting the clinical association between serum ferritin concentrations and diabetes, it is not clearly identified in other ethnic groups besides western population. This study analyzed a longitudinal relationship between serum ferritin concentration and the risk for diabetes in non-diabetic Korean men.This study was composed of a cohort of 30,002 non-diabetic Korean men who participated in medical health check-up program in 2005. They were divided into 4 groups according to their baseline ferritin concentrations (first quartile–fourth quartile) and monitored until 2010. Their incidences and hazard ratios of diabetes were compared among 4 groups according to their baseline ferritin concentrations.While 2655 cases of diabetes newly developed during follow-up, incidence of diabetes increased proportionally to the baseline serum ferritin concentrations. In Cox-proportional hazard model, hazard ratios for diabetes also independently increased according to the baseline serum ferritin concentrations [quartile 1: 1.00 (reference), quartile 2: 1.00 (0.87–1.12), quartile 3: 1.13 (1.00–1.29), quartile 4: 1.18 (1.04–1.34), respectively].Increased ferritin concentration was associated with increased risk for diabetes in Korean men. These findings suggest the clinical significance of serum ferritin concentration in the development diabetes.