D-dimer is a primary degradation product of cross-linked fibrin, and can be an effective diagnostic factor of venous thromboembolism. However, its prognostic role in patients with acute ST-segment elevation myocardial infarction (STEMI) remains controversial. This study aimed to investigate whether D-dimer has a predictive value for long-term prognosis in patients with STEMI.We retrospectively enrolled 872 STEMI patients treated with primary percutaneous coronary intervention. Patients were divided into quartiles according to their admission D-dimer increased multiple, with the highest quartile (G4) (n = 219) defined as increased multiple ≧1.33, and the lowest quartile (G1) (n = 215) as increased multiple ≦0.33.Compared with G1, higher in-hospital heart failure (40.2% vs 10.2%, P < .0001), malignant arrhythmia (14.2% vs 2.3%, P < .0001), and all-cause mortality (5.9% vs 0%, P < .0001) rates were observed in G4. After a follow-up period of 29 months, 84 patients had died. In the Cox multivariate analysis, a high admission D-dimer increased multiple (≧1.33) was found to be an independent predictor of all-cause mortality (hazards ratio: 2.53, 95% confidence interval: 1.02-6.26, P = .045).Thus, there was an association between a high D-dimer level and the increase in in-hospital major adverse cardiovascular events, such as heart failure, malignant arrhythmias, and death. High D-dimer level was also an independent predictor of long-term all-cause mortality.