To evaluate the acute phase (pre- and in-hospital) antithrombotic management patterns (AMPs) and in-hospital outcomes for patients hospitalized with an acute coronary syndrome (ACS).In total, 1034 patients [514 patients with ST-segment elevation myocardial infarction (STEMI) and 520 with unstable angina/non-STEMI (UA/NSTEMI)] hospitalized for ACS within 24 h of symptom onset were included in this multicenter prospective registry study conducted at 34 hospitals across Turkey. Patient characteristics, index event description, pre- and in-hospital AMPs, and clinical outcomes were evaluated.Majority (89.1%) of patients did not receive pre-hospital treatment. Overall 87.9% patients with STEMI and 55.6% patients with NSTEMI underwent percutaneous coronary intervention and dual antiplatelet therapy (DAPT) was based mainly on acetylsalicylic acid (ASA) and clopidogrel during hospitalization (99.8% and 98.2%, respectively). DAPT use at discharge was 98.4% and 86.8%, respectively. The percentage of patients with STEMI who received pre-hospital care, in-hospital cardiac catheterization, and pre and/or in-hospital triple antiplatelet therapy was higher than that of patients with UA/NSTEMI. In addition, higher rate of in-hospital hemorrhagic (2.3% vs. 0.8%) and cardiac ischemic (1.2% vs. 0.4% for MI and 1.6% vs. 0.8% for recurrent ischemia) complications and earlier induction of pre and/or in hospital antiplatelet therapy and cardiac catheterization were also noted in patients with STEMI than in those with UA/NSTEMI.Our findings revealed in-hospital and at-discharge management to be mainly based on DAPT in patients with ACS. Interventional strategies were used in the majority of patients with STEMI, while the usage and timing of immediate pre-hospital ECG from symptom onset should be improved in these patients.