Resistin, which is derived from the gene of RSTN, belongs to a family of cysteine-rich secretory proteins called resistin-like molecules (RELMs). Increased serum resistin levels are associated with coronary artery disease (CAD) and the risk of cardiovascular death. Patients (n = 214) with an initial diagnosis of stable angina pectoris, unstable angina pectoris, and myocardial infarction without ST-segment elevation and referred to catheter laboratory for coronary angiography were enrolled in the study. We aimed to investigate the relationship between increased serum resistin level and CAD. The severity of CAD was calculated by the Gensini scoring system. In conclusion, we established a significant correlation between serum resistin levels and CAD (P = .010). Also, serum resistin levels correlated with the Gensini score that represents the severity of CAD angiographically (P = .010).