Objective Diabetes mellitus (DM) and thyroid dysfunction have been shown to mutually influence each other and associations between both conditions. The present study was to evaluate the thyroid parameters in DM risk and non-DM risk subjects and observed that abnormalities of thyroid hormones were associated with DM. Methods In this study subjects consisted of 355 Korean adult men with subclinical thyroid dysfunction (hypothyroidism and hyperthyroidism) divided into two groups: 225 subjects with DM risk (fasting blood sugar (FBS) ≥ 100 mg/dL or receving treatment such as insulin, anti-diabetic drug) and 130 subjects without DM risk. Subjects were evaluated anthropometry and biochemical parameters. Results In DM risk group, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), FBS, HbA1c, triglyceride (TG) and thyroid stimulating hormone (TSH) were higher than non-DM risk groupafter adjustment of age (P < 0.05). TSH level was ositively correlated with SBP (r = 0.141, P < 0.01), DBP (r = 0.148, P < 0.01), TC (r = 0.233, P < 0.001), LDL (r = 0.198, P < 0.01) after adjustment of age. Higher TSH concentration was found to be an independent risk factor for DM risk in thyroid dysfuntion after adjustment of age (odds ratio 1.06, 95% CI 1.01~1.11; P = 0.044). The risk of DM increased with higher FT4 in subclinical hyperthyroidism after adjustment of age (odds ratio 4.94, 95% CI 4.94~16.60; P = 0.010). Conclusion Thyroid dysfunction is associated with an increased risk of DM especially in those with higher TSH levels. Therefore, further prospective studies with larger number of subjects are required to strengthen the observations of this study.