Cardiac troponins (cTn) are routinely measured for the diagnosis and prognosis of myocardial infarction (MI). The relation between troponin levels, estimated glomerular filtration rate (eGFR), postinfarction heart failure (HF), and mortality is unclear in patients with kidney impairment. This is a retrospective, cross-sectional study of patients presenting to the Emergency Department at a single tertiary center. Participants presenting with confirmed type I MI from January 1, 2019, to December 31, 2021, were analyzed from the Myocardial Ischemia National Audit Project database. Main outcomes were acute HF, measured using Killip class, and inpatient mortality. Peak cardiac troponin T (cTnT) level was a secondary outcome. Data on 2,815 patients (67±14 years, 28% female) were analyzed. Ordinal logistic regression analysis was used to test for predictors of increasing Killip class. Binary logistic regression was used to test for predictors of inpatient mortality. Analysis of a sub-sample matched for age and diabetes mellitus status showed increased mortality in patients with eGFR <60 ml/min/1.73 m² (12.2% vs 4.4%, p <0.001). Multivariate predictors of acute HF included log-transformed peak cTnT, eGFR, body mass index (BMI), and diabetes mellitus status. Multivariate predictors of inpatient mortality included log-transformed peak cTnT, eGFR, age, BMI, and Killip class 3/4. On multivariate analysis, eGFR, ST-elevation MI diagnosis, BMI, male gender, diabetes mellitus status, and hypertension were all predictive of peak cTnT after MI. In conclusion, peak cTnT level and eGFR at presentation after MI are independent predictors of acute HF severity and death in patients with and without kidney impairment.