Sasang Constitutional Medicine, which is a branch of traditional Korean medicine, states that medications for diabetes should be individualized according to the patient's individual constitution. However, the effect of constitution on diabetes has not been evaluated to date. Therefore, this study was conducted to determine if constitution is an independent risk factor for diabetes by comparing the prevalence and odds ratios (ORs) of the disease according to constitution. The medical records of 1443 adults who had been examined and classified based on their constitution at Kyung Hee University Hospital in Seoul, Korea were reviewed. A chi-squared test and Fisher's exact test were used to compare the prevalence of diabetes according to constitution, and multiple logistic regression was used to calculate the ORs for diabetes. The prevalence of diabetes differed significantly according to constitution (Χ2 = 36.20, df = 2, P < 0.001). Specifically, the prevalence of the disease was higher in Tae-eumin (11.4%) individuals than in Soyangin (5.0%) or Soeumin (1.7%) individuals. In addition, multiple logistic regression revealed that Tae-eumin individuals had a greater risk for diabetes than Soeumin individuals. When compared to Soeumin individuals, the adjusted ORs were 2.01 (95% CI 0.77–5.26) for Soyangin individuals and 3.96 (95% CI 1.48–10.60) for Tae-eumin individuals. These results show that constitution has a significant and independent association with diabetes, which suggests that constitution is an independent risk factor for diabetes that should be considered when attempting to detect and prevent the disease.