Health care costs increase with prolonged in-hospital stays. Many factors influence the length of stay for patients with ST-elevation myocardial infarction (STEMI). In this study, we aimed to determine the differences between long-stay and early discharged patients with STEMI. For this retrospective study, a total of 2486 consecutive patients with STEMI (mean age: 56.2 ± 11.7 years, 16.5% female) who had undergone primary percutaneous coronary intervention (pPCI) were enrolled. Patients were divided into 2 groups based on mean in-hospital stay: <6 days and ≥6 days. Anterior STEMI (odds ratio [OR]: 1.61, 95% confidence interval [CI]: 1.02-2.54; P = 0.03), angiographic failure (OR: 2.89, 95% CI: 1.19-7.01; P = .01), and peripheral vascular complications (PVCs; OR: 4.18, 95% CI: 1.16-15.03; P = .02) were found to be independent predictors of ≥6-day in-hospital stay. The incidence of long-term total mortality and composite end point for death, reinfarction, and target vessel revascularization were significantly higher in ≥6-day in-hospital stay patients. Anterior STEMI, angiographic failure, and PVCs were found to be independently associated with prolonged in-hospital stay for patients with STEMI following pPCI.