OBJECTIVE: Anger may cause adverse cardiovascular responses, but the effects of anger management on clinical cardiovascular outcomes are insufficiently understood. We sought to assess the influence of anger management through a cognitive behavioral intervention on endothelial function in patients with a recent myocardial infarction (MI). METHODS: Patients with ST-elevation MI and a low anger control score were enrolled during hospitalization in a randomized, parallel, controlled clinical trial. Intervention was anger management with cognitive behavioral techniques implemented by a psychologist in two individual monthly sessions. The primary end point was the between-group difference in the variation of flow-mediated dilation (FMD) in the brachial artery from baseline to the 3-month follow-up. The second end point comprised major cardiovascular events at 24-month follow-up. RESULTS: A total of 43 patients (age = 56 [9] years; 23.3% women) were randomized to the intervention group and 47 patients (age = 58 [10] years; 19.1% women) to the control group. Baseline clinical characteristics were not statistically different between groups. Both groups showed a significant improvement in anger control from baseline to end point; however, the difference in intergroup variation was not statistically significant. The difference in FMD variation from baseline to the 3-month follow-up was significantly higher in the intervention group. The partial η2 was 0.057 (p = .024), indicating a medium effect size. There was no difference between groups regarding major cardiovascular events. CONCLUSIONS: Anger management by cognitive behavioral techniques may improve endothelial function in post-MI patients with low anger control, but it remains unclear via which mechanism these effects occurred. Further studies with larger numbers of patients, assessments of changes in anger, improved comparability of preintervention FMD, and longer follow-up are warranted.Trial Registration:ClinicalTrials.gov identifier: NCT02868216.