Objective To evaluate the incidence and possible risk factors of clopidogrel resistance in elderly patients with diabetes and coronary heart disease treated with percutaneous coronary intervention, and to investigate the impact of clopidogrel resistance on post-procedural outcomes. Methods Total 232 elderly inpatients with diabetes and coronary heart disease who were treated with clopidogrel and percutaneous coronary intervention were consecutively enrolled in this study. After receiving TEG test, the patients were divided into two groups according to ADP dependent platelet inhibition ratio: the control group (ratio＞50%) and the study group (ratio＜50%). The profiles of clinical cardiovascular risk factors, lipid and glucose metabolic indices, inflammation indices were collected before coronary intervention and compared between two groups. The incidence of post-procedural in-hospital myocardial infarction and mortality were also compared between two groups. Results There was no difference in age, gender, body mass index, history of smoking, incidences of hypertension and hyperlipidermia, medication, levels of triglyceride, total cholesterol, low density lipoprotein cholesterol and hemoglobin A1c between two groups. The patients in study group had lower level of high density lipoprotein cholesterol(HDL-C) and higher levels of fasting glucose, glucosylated serum protein(GSP) and high sensitivity C reactive protein(hs-CRP) than patients in control group (P＜0.01 for all). The study group had higher rate of post-procedural myocardial infarction than the control group (P＜0.01). No difference of mortality rate was found between two groups. Conclusions Clopidogrel resistance is common in elderly patients with diabetes and coronary heart disease. Elderly patients with clopidogrel resistance showed higher risk of in-hospital myocardial infarction after coronary intervention. Elevated levels of fasting glucose, GSP and hs-CRP and low level of HDL-C may suggest high risk of clopidogrel resistance in elderly patients with diabetes and coronary heart disease.