OBJECTIVE: Acute coronary syndrome (ACS) is one of the leading causes of mortality, globally. Atherosclerosis is an under lying factor in ACS process and coagulative cascade is activated secondary to atherosclerotic plaque rupture. Fibrinopeptide A (FPA) takes an active role in thrombus formation and is an indicator of coagulative process. We aimed to evaluate serum FPA level in patients with ACS. METHODS: Patients diagnosed with ACS and chronic coronary syndrome (CCS), with non-obstructive coronary artery dis ease as a control group, were included in the study. Blood samples and demographic data of all patients were obtained at admission. Obtained data were compared between ACS and control groups. RESULTS: The study consisted of 107 patients with ACS and 69 patients with CCS. ACS group was older (p<0.001) with male preponderance (p<0.001), more likely to had hypertension (p<0.001), and had a higher smoking rate (p<0.001). Serum FPA level was highest in the ST elevated myocardial infarction group (p<0.001). FPA>3.38 ng/mL predicted ACS with 89.7% sensitivity and 78% specificity (AUC: 0.825, 95% CI 0.745–0.905; p<0.001). CONCLUSION: Serum FPA may be used for the differential diagnosis of ACS. In addition, patients with increased FPA may be considered to be given more aggressive antithrombotic medication.