Whether serum triglyceride level correlates with clinical outcomes of patients with ST segment elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (pPCI) remains unclear. From June 2008 to February 2012, all patients with STEMI who were treated with pPCI in this tertiary referral hospital and then had fasting lipid profiles measured within 24 hours were included and dichotomized into lower- (≦ 150 mg/dl) and higher-triglyceridemic (>150 mg/dl) groups. Baseline characteristics, in-hospital outcomes, and late major adverse cardiovascular events (MACE) were compared in-between. Independent predictors for in-hospital death and late adverse events were identified by multivariate logistic and Cox regression analyses. A total of 247 patients were enrolled, including 163 lower-triglyceridemic and 84 higher-triglyceridemic subjects. The angiographic characteristics, pPCI results and in-hospital outcomes were similar between the two groups. However, multivariate logistic analysis identified triglyceride level as a negative predictor for in-hospital death (OR 0.963, 95% CI 0.931-0.995, p = 0.023). At follow-up for a mean period of 1.23 to 1.40 years, compared with the high-triglyceridemic group, low-triglyceridemic patients had fewer cumulative incidences of target vessel revascularization (TVR) (21.7% vs. 9.5%, p = 0.011) and overall MACE (26.1% vs. 11.9%, p = 0.0137). Cox regression analysis confirmed serum triglyceride as a negative predictor for TVR and overall MACE. Serum triglyceride level inversely correlates with in-hospital death and late outcomes in patients with STEMI treated with pPCI. Thus, when managing such patients, a high serum triglyceride level can be regarded as a benign factor but not a target for aggressive therapy.