Background Myocardial injury in patients with COVID‐19 is associated with increased mortality during index hospitalization; however, the relationship to long‐term sequelae of SARS‐CoV‐2 is unknown. This study assessed the relationship between myocardial injury (high‐sensitivity cardiac troponin T level) during index hospitalization for COVID‐19 and longer‐term outcomes. Methods and Results This is a prospective cohort of patients who were hospitalized at a single center between March and May 2020 with SARS‐CoV‐2. Cardiac biomarkers were systematically collected. Outcomes were adjudicated and stratified on the basis of myocardial injury. The study cohort includes 483 patients who had high‐sensitivity cardiac troponin T data during their index hospitalization. During index hospitalization, 91 (18.8%) died, 70 (14.4%) had thrombotic complications, and 126 (25.6%) had cardiovascular complications. By 12 months, 107 (22.2%) died. During index hospitalization, 301 (62.3%) had cardiac injury (high‐sensitivity cardiac troponin T≧14 ng/L); these patients had 28.6%, 32.2%, and 33.2% mortality during index hospitalization, at 6 months, and at 12 months, respectively, compared with 4.1%, 4.9%, and 4.9% mortality for those with low‐level positive troponin and 0%, 0%, and 0% for those with undetectable troponin. Of 392 (81.2%) patients who survived the index hospitalization, 94 (24%) had at least 1 readmission within 12 months, of whom 61 (65%) had myocardial injury during the index hospitalization. Of 377 (96%) patients who were alive and had follow‐up after the index hospitalization, 211 (56%) patients had a documented, detailed clinical assessment at 6 months. A total of 78 of 211 (37.0%) had ongoing COVID‐19–related symptoms; 34 of 211 (16.1%) had neurocognitive decline, 8 of 211 (3.8%) had increased supplemental oxygen requirements, and 42 of 211 (19.9%) had worsening functional status. Conclusions Myocardial injury during index hospitalization for COVID‐19 was associated with increased mortality and may predict who are more likely to have postacute sequelae of COVID‐19. Among patients who survived their index hospitalization, the incremental mortality through 12 months was low, even among troponin‐positive patients.