Objective To determine the effect of subclinical hypothyroidism (SHT) on diabetic macrovascular diseases in the elderly with type 2 diabetes mellitus. Methods Among the 368 type 2 diabetic subjects who admitted in our department from June 2013 to June 2015, 35 subjects complicated with SHT (aged over 60 years) and 35 matched subjects without SHT were selected and enrolled in this study．Fasting plasma glucose (FPG), total cholesterol (TC), triglycerides (TG), left ventricular ejection fraction (LVEF), and E/A ratio [left ventricular early diastolic mitral flow velocity (E) to left ventricular end diastolic mitral flow velocity (A)] and ankle-brachial index (ABI) were compared between the 2 groups in order to determine the effect of SHT on diabetic macrovascular diseases. Results The serum levels of thyroid stimulating hormone (TSH, P＜0.001) and TC (P＝0.002) were significantly higher, while LVEF was obviously lower (P＝0.043) in the SHT group than in the euthyroid group. But there were no remarkable differences in the the E/A ratio and ABI between the 2 groups (P＞0.05). Conclusion Subclinical hypothyroidism may cause left ventricular systolic dysfunction in the elderly with type 2 diabetes mellitus, but its effect on diabetic macrovascular diseases needs further investigation.