Objectives: We investigated the relationship between coagulation assessed by thromboelastography (TEG) and myocardial damage in ST-segment elevation myocardial infarction (STEMI). Methods: We measured platelet activity with TEG-maximum amplitude (TEG-MA) in 233 patients undergoing urgent percutaneous coronary intervention (PCI). Infarct size and myocardial salvage index were evaluated using cardiac magnetic resonance, and the relation of these parameters to posttreatment coagulation was examined retrospectively. Adverse events were adjudicated and related to the coagulation status during the index event. Results: Hypercoagulation was found in 82 (35.2%) patients and was neither correlated to infarct size nor correlated to myocardial salvage index (P = .28 and .65, respectively) or clinical adverse events. Patients who experienced an adverse event during follow-up had a slightly higher TEG-MA value than patients with an event-free follow-up, but this was not statistically significant (68.1 vs 67.3, P = .44). Conclusions: The TEG-MA does not appear to be a sensitive predictor of reperfusion success and prognosis in urgent PCI for STEMI.