Many studies have shown the prognostic significance of glycated hemoglobin (HbA1c) for overall coronary artery disease (CAD). But less is known about the role that HbA1c played in the prognosis of patients diagnosed with ST-segment elevation myocardial infarction (STEMI). Results from previous studies were controversial. Therefore, a meta-analysis was conducted to investigate whether admission HbA1c level was a predictor of short- and long-term mortality rates among patients diagnosed with STEMI. Relevant literatures were retrieved from the electronic databases up to March 2016. Reference lists were hand searched to identify eligible studies. Articles were included if they provided sufficient information for the calculation of pooled relative risk (RR) and its corresponding 95% confidence interval (CI). Finally, we got 19 prospective studies involving a total of 35,994 STEMI patients to evaluate the associations between HbA1c level and their in-hospital, 30-day and long-term mortality. Among STEMI patients, HbA1c level was not significantly associated with in-hospital mortality (RR 1.20, 95% CI 0.95-1.53, p=0.13). However, elevated HbA1c level was positively associated with risk of 30-day and long-term mortality (for 30-day mortality, RR 1.25, 95% CI 1.03-1.52, p=0.02; for long-term mortality, RR 1.45, 95% CI 1.20-1.76, p<0.01). In conclusion, our findings suggested elevated HbA1c level among STEMI patients was an indicator of 1.25-fold 30-day mortality risk and 1.45-fold long-term mortality risk, respectively. STEMI patients with high HbA1c level should have their chronic glucose dysregulation under intensive control.