Aims: To investigate the association of serum ferritin levels and ferritin level changes with the 10-year risk of new-onset type 2 diabetes mellitus (T2DM). Methods: Among 2359 subjects without T2DM at baseline in 2002, 1956 subjects were re-examined in 2007, and 1660 subjects were invited to be re-examined in 2012. Serum ferritin (ng/ml) levels were measured by latex-enhanced turbidimetric immunoassay. Five-year serum ferritin changes were categorized into four groups using the median as the cut-off point. Multivariate logistic regression was performed to examine the independent association of serum ferritin levels and 5-year ferritin level changes with 10-year new-onset T2DM. Results: At the 10-year follow-up, 205 (12.3%) subjects had developed new-onset T2DM. After adjusting for traditional risk factors and high-sensitivity C-reactive protein, 10-year new-onset T2DM risk was significantly increased in subjects in the highest tertile of baseline serum ferritin levels [ odds ratio (OR) = 1.80, 95% confidence interval (CI): 1.17-2.79] and in subjects with high serum ferritin levels in both 2002 and 2007 (OR = 1.54, 95% CI: 1.012.34). After adjusting for baseline fasting blood glucose, the effect was attenuated and became borderline or non-significant. Conclusions: Serum ferritin levels and ferritin level changes were associated with 10-year new-onset T2DM risk in the Chinese population, whereas the independent effect awaits validation from studies with larger sample sizes. (C) 2017 Elsevier B.V. All rights reserved.