Background: Although much is known about the prognostic value of the GRACE risk score, there are few studies investigating how it relates with the angiographic complexity of coronary artery disease. For this reason, in this study, we aimed to assess the predictive capacity of the GRACE score in acute coronary syndrome in respect to the angiographic complexity based on the SYNTAX score. Methods: A cross-sectional study of patients with acute coronary syndrome undergoing coronary angiography during hospitalization, with at least one ≥50% stenotic lesion in vessels ≥1.5mm in diameter. Complex coronary artery disease was defined as SYNTAX ≥23. Results: This study investigated 183 patients. A positive correlation was observed between the GRACE and the SYNTAX scores (p=0.005), however the association was weak (r=0.20). The GRACE score showed discriminatory capacity between patients with and without complex coronary artery disease, however the relevance was low, with an area under the ROC curve of 0.59 (95%CI: 0.51-0.67; p=0.042). Conclusion:The GRACE risk score is not a sufficiently accurate predictor of angiographic complexity in acute coronary syndrome.