Objective: NSAID-activated gene-1 (NAG-1) is a protein that belongs to the transforming growth factor β superfamily. An elevated serum level of NAG-1 was found to be associated with type 2 diabetes mellitus (T2DM). In this study, we investigated the role of NAG-1 in progression of type 2 diabetes from prediabetes through 5 year prospective study. Methods: The participants are people of DalSeong-gun cohort in Korea. We examined the metabolic parameters and 75 g oral glucose tolerance test twice in 2003 and 2008. According to change in 2008 from prediabetes in 2003, we divided the patients as three groups. Group 1 is defined as normal glucose tolerance from prediabetes. Group 2 is persistent prediabetes during 5 years, Group 3 is defined as diabetic progression from prediabetes. We analyzed the change of metabolic parameters and the change of NAG-1 levels. Results: In 2003, Newly found diabetic patients were 12.2% (216/1773), prediabetes were 22.7% (402/1773, IFG 15.3%, IGT 3.7%, both 3.7%). Group 3 showed significant higher BMI (Group1; 23.83 ± 2.74, Group2; 23.97 ± 2.93, Group3; 25.31 ± 3.03 kg/m2) and waist hip ratio (Group 1; 0.89 ± 0.07, Group 2; 0.90 ± 0.64, Group 3; 0.92 ± 0.06) than Group 1 and Group 2. Furthermore, Group 3 presented higher NAG-1 level than Group 1 and Group 2. (Group 1; 719.64 ± 411.53, Group2; 885.51 ± 529.13, Group 3; 1066.27 ± 681.81 pg/mL). Conclusion: The prediabetes with higher NAG-1 level progressed to diabetes by the 5 years following study. Thus NAG-1 may be useful marker to classify the high risk prediabetic patients.