We investigated the association between platelet-to-lymphocyte ratio (PLR) and clinical outcomes (including all-cause mortality, recurrent myocardial infarction, heart failure, serious cardiac arrhythmias and ischemic stroke) in patients with ST-segment elevation myocardial infarction (STEMI). Based on PLR quartiles, 5886 patients with STEMI were categorized into 4 groups: <98.8 (n = 1470), 98.8 to 125.9 (n = 1474), 126.0 to 163.3 (n = 1478), >163.3 (n = 1464), respectively. We used Cox proportional hazards models to examine the relation between PLR and clinical outcomes. Mean duration of follow-up was 81.6 months, and 948 patients (16.1%) died during follow-up. The lowest mortality occurred in the lowest PLR quartile group (P = 0.006), with an adjusted hazard ratio of 1.18 (95% confidence interval [CI], 1.04-1.55), 1.31 (95% CI, 1.18-1.64), and 1.59 (95% CI, 1.33-1.94) in patients with PLR of 98.8 to 125.9, 126.0 to 163.3, >163.3, respectively. Higher levels of PLR were also associated with recurrent myocardial infarction (P-trend = .023), heart failure (P-trend = .018), and ischemic stroke (P-trend = .043). In conclusion, a higher PLR was associated with recurrent myocardial infarction, heart failure, ischemic stroke, and all-cause mortality in patients with STEMI.