Background: This study investigated the association between thyroid function and the 10-year cardiovascular disease (CVD) risk in patients with diabetes. Methods: This retrospective cross-sectional study analyzed 246 patients with diabetes aged 30 to 79 years (weighted n=1,611,708) from the 2013 to 2014 Korea National Health and Nutrition Examination Survey. Individuals with a history of CVD, thyroid disease, or pregnancy were excluded. Thyroid function was categorized as euthyroid, hypothyroid, or hyperthyroid, based on serum thyroid-stimulating hormone (TSH) levels (reference in Koreans, 0.62–6.86 mIU/L). The 10-year CVD risk was estimated using the Predicting Risk of CVD EVENTs calculator. Results: The mean participant age was 54.3±10.1 years, with a male-to-female ratio of 1.41:1. Although patients with hypothyroid (14.1%) and hyperthyroid (15.7%) statuses showed a higher CVD risk than those with euthyroid status (12.3%), the difference was not statistically significant (p=0.337). However, in the hypothyroid group (n=11), TSH levels showed a moderate correlation with 10-year CVD risk (r=0.603, p<0.05), although this finding should be interpreted with caution owing to the small sample size. After adjusting for diabetes- and thyroid-related variables, TSH level was independently associated with higher estimated 10-year CVD risk, particularly in patients with a glycated hemoglobin level of <7% (adjusted coefficient, 0.17; 95% confidence interval, 0.05–0.29; p<0.05). Conclusion Monitoring TSH levels in patients with well-controlled diabetes may provide additional information regarding the risk of CVD; however, prospective studies are needed to confirm the long-term prognostic value.