Leukocytes are reported as crucial not only for plaque activation but also in thrombus formation in acute coronary syndromes (ACSs). Among the markers of inflammation, in coronary artery disease neutrophil-lymphocyte ratio (NLR) has been reported to have the greatest predictive power of poor outcomes. Our aim was to evaluate the association of NLR with coronary thrombus in patients with non-ST-segment elevated ACSs (NST-ACSs). A total of 251 patients were hospitalized with a diagnosis of NST-ACS including non-ST-segment elevated myocardial infarction and unstable angina pectoris. Coronary angiographies were performed. In 167 patients, coronary thrombus was detected. Between the patient groups with and without coronary thrombus, neutrophil count, platelet count, and NLR are significantly increased, and lymphocyte count is significantly decreased in the group with coronary thrombus as compared to patient group without coronary thrombus. Leukocyte count and NLR may give an indication about the presence of coronary thrombus. In NST-ACS, blood parameters may give valuable information about the status of the coronary arteries.