Background: Diabetic retinopathy (DR) was found to be associated with an increased risk for coronary artery disease (CAD). However, there are less data about the relation between the degree of DR and the angiographic severity of CAD. Objective: The objective of the study is to examine the relation between the degree of DR and the angiographic severity of CAD in patients with acute coronary syndrome (ACS). Patients and Methods: Fifty diabetic patients with ACS were enrolled in this study. History, clinical examination, echocardiography, coronary angiography, and fundus examination were done to all patients. According to the degree of DR, patients were classified into two groups: Group I – patients with no or mild nonproliferative (NP) DR (n = 27) and Group II – patients with moderate or severe NP DR or with proliferative DR (n = 23). Results: Population characteristics, risk factors, diabetes duration, insulin use, and echocardiographic measures were comparable in the two groups. Patients in Group II had significantly more number of diseased vessels, more maximum stenosis, and higher Gensini score than those of Group I. There was a significant correlation between the degree of DR and the number of diseased vessels (r = 0.358, P = 0.011) and highly significant correlation between the degree of DR and maximum stenosis (r = 0.452, P = 0.001) and Gensini score (r = 0.706, P < 0.00001). Conclusion: There is an obvious relation between the degree of DR and angiographic severity of CAD in diabetic patients with ACS. Patients with a higher degree of DR had more severe CAD. Keywords: Acute coronary syndrome, coronary angiography, diabetic retinopathy