Background: Acute coronary syndrome (ACS) is associated with activation of platelets and the coagulation system which could influence the incidence of early stent thrombosis (EST). We aimed to determine the incidence and predictors of EST in patients undergoing coronary stenting during ACS. Methods: The study comprised 1202 consecutive patients, drawn from a nationwide ACS survey, who underwent coronary stenting during ACS and were followed up for 30 days. Early stent thrombosis was based on the Academic Research Consortium definition. Results: Thirty patients (2.5%) sustained EST. The occurrence of EST in patients with unstable angina/non-ST-elevation myocardial infarction and ST-elevation myocardial infarction (STEMI) was 0.9% and 3.9%, respectively (P < .05), and was even higher (5.2%) in STEMI patients who underwent primary percutaneous coronary intervention. On multivariate analysis, STEMI (OR 6.3, 95% CI 2.1-18, P = .0008), multivessel disease (OR 5.9, 95% CI 1.9-21, P = .003) and Killip class ≥2 (OR 2.9, 95% CI 1.3-6.6, P = .008) were independent correlates of EST. The use of bare versus drug-eluting stents was not associated with any significant difference in EST. Conclusions: Patients presenting with STEMI who are hemodynamically unstable and have multivessel coronary disease undergoing coronary stenting during ACS, are at increased risk of EST.