Background: Coronavirus Disease 2019 (COVID-19) is associated with many clinical manifestations including respiratory failure and cardiovascular compromise. Objectives: We examine outcomes in critically ill individuals with COVID-19 who develop atrial tachyarrhythmias (ATA). Methods: We collected data from electrocardiograms and the electronic medical record of COVID-19 positive (COVID+) and negative (COVID-) individuals admitted to our medical intensive care unit between February 29 and June 28, 2020. We compared clinical and demographic characteristics, new onset ATA, hemodynamic compromise (HC) following ATA, and in-hospital mortality in those who were COVID+ vs. COVID-. HC was defined as having a new or increased vasopressor requirement or the need for direct current cardioversion for hemodynamic instability within 1 hour of ATA onset. Results: Of 300 individuals included, 200 were COVID+ and 100 were COVID-. Mean age was 60±16 years, 180 (60%) were males, and 170 (57%) were African American. New onset ATA occurred in 16% of COVID+ and 19% of COVID- individuals (p=0.51). When compared to COVID- participants without ATA, COVID+ individuals with new onset ATA had higher mortality after multivariable adjustment (OR 5.0, 95% CI 1.9-13.5). New onset ATA was followed by HC in 18 COVID+ but no COVID- participants (P=0.0001). COVID+ individuals with HC after ATA were requiring high levels of ventilatory support at the time of ATA onset. Conclusions: ATA may be an important mediator of HC in critically ill individuals with COVID-19, especially for those mechanically ventilated. Recognition of this could assist with clinical care and prognostication for individuals with COVID-19.