Aims/Introduction: Sasang constitutional medicine (SCM) has existed in traditional Korean medicine for more than 100 years. SCM consists of four different types: So-Eum (SE), So-Yang (SY), Tae-Eum (TE) and Tae-Yang (TY). It is of great importance that the Sasang constitution type (SCT) be evaluated accurately and recognized by medical communities. Materials and Methods: From the Ansung-Ansan prospective cohort study, 10,038 participants were recruited from the years 2001-2002. Of 10,038 original participants, 2,460 participants underwent SCT evaluation. The Cox proportional hazard model was used to predict diabetes during the 10-year follow-up period. Results: During 10 years of follow up (22,007 person-years), 472 incidence cases (215/10,000 Incidence Density) of type 2 diabetes mellitus were documented. We identified that the TE group was significantly older, more obese, and had higher blood pressure, glucose metabolic values and lipid profiles levels. Relative risk (RR) and 95% confident intervals (CI) for type 2 diabetes were 1.696 (95% CI 1.204-2.39, P = 0.003) for TE when compared with the SE type. After controlling all potential confounders, the Cox proportional hazard model showed that RR was 1.635 (95% CI 1.111-2.406) in non-obese (body mass index <25) TE, and RR was 1.725 (95% CI 1.213-2.452) in obese (body mass index ≥25) TE when compared with the SE type. We did not find any differences when comparing SE and SY types. The findings shows that TE is a higher risk factor for type 2 Diabetes, independent of obesity level. Conclusions: The present study suggests that the TE type, independent of obesity level, is a strong risk factor of type 2 diabetes.