Background: Osteoprotegerin (OPG) is a glycoprotein with a regulatory role in immune, skeletal and vascular systems. Data suggest that high circulating OPG levels are associated with an increased risk of cardiovascular disease. We analyzed the association between OPG and long-term outcome in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). Methods: We included 716 consecutive STEMI patients admitted to a single high-volume invasive heart center from September 2006 to December 2008. Endpoints were all-cause mortality, repeat myocardial infarction, admission due to heart failure and combinations thereof. Median follow-up lasted 27 months (interquartile range: 22-33). Results: OPG levels exhibited a non-Gaussian distribution and were therefore divided into quartiles. High levels of OPG were significantly associated with a worse outcome. After adjustment for conventional risk factors (e.g. C-reactive protein, estimated glomerular filtration rate, symptom-to-balloon time and troponin I) using Cox regression, OPG remained a significantly independent predictor of death (HR per increase in OPG quartile: 1.28; CI: 1.03-1.59; p = 0.03), repeat myocardial infarction (HR: 1.30; CI: 1.00-1.68; p = 0.05) and admission with heart failure (HR: 1.50; CI: 1.18-1.90; p = 0.001). Conclusion: This study shows that OPG independently predicts long-term outcome in STEMI patients treated with pPCI. Eventually, this knowledge could improve risk stratification and overall outcome.