The cardiovascular safety from azithromycin in the treatment of several infectious diseases has been challenged. In this prespecified pooled analysis of 2 multicenter randomized clinical trials, we aimed to assess whether the use of azithromycin might lead to corrected QT (QTc) interval prolongation or clinically relevant ventricular arrhythmias. In the COALITION COVID Brazil I trial, 667 patients admitted with moderate COVID-19 were randomly allocated to hydroxychloroquine, hydroxychloroquine plus azithromycin, or standard of care. In the COALITION COVID Brazil II trial, 447 patients with severe COVID-19 were randomly allocated to hydroxychloroquine alone versus hydroxychloroquine plus azithromycin. The principal end point for the present analysis was the composite of death, resuscitated cardiac arrest, or ventricular arrhythmias. The addition of azithromycin to hydroxychloroquine did not result in any prolongation of the QTc interval (425.8 ± 3.6 ms vs 427.9 ± 3.9 ms, respectively, mean difference -2.1 ms, 95% confidence interval -12.5 to 8.4 ms, p = 0.70). The combination of azithromycin plus hydroxychloroquine compared with hydroxychloroquine alone did not result in increased risk of the primary end point (proportion of patients with events at 15 days 17.2% vs 16.0%, respectively, hazard ratio 1.08, 95% confidence interval 0.78 to 1.49, p = 0.65). In conclusion, in patients hospitalized with COVID-19 already receiving standard-of-care management (including hydroxychloroquine), the addition of azithromycin did not result in the prolongation of the QTc interval or increase in cardiovascular adverse events. Because azithromycin is among the most commonly prescribed antimicrobial agents, our results may inform clinical practice. Clinical Trial Registration: NCT04322123, NCT04321278.