Introduction: New onset atrial fibrillation leads to worse outcomes in patients with sepsis. The association between new onset atrial fibrillation (AF) in COVID19 patients with COVID19 outcomes are lacking. This study aims to determine whether new onset atrial fibrillation in COVID19 patients admitted in the ICU is a risk factor for death or requirement of mechanical ventilation (MV). Methods: This is a retrospective study conducted in a cohort of COVID-19 patients admitted to Bahrain Defence Force COVID19 Field ICU between April 2020 to November 2020. Data were extracted from the electronic medical records. The patients who developed new onset AF during admission were compared to patients who remained in sinus rhythm. Multivariate logistic regression models were used to control for confounders and estimate the effect of AF on the outcomes of these patients. Results: Our study included a total of 492 patients out of which 30 were diagnosed with new onset AF. In the AF group, the primary outcome occurred in 66.7% of patients (n = 20). In the control group, 17.1% (n = 79) developed the primary outcome. Upon adjusting for the confounders in the multivariate regression model, AF had an odds ratio of 3.96 (95% CI: 1.05-14.98; p = 0.042) for the primary outcome. Conclusion: Our results indicate that new onset AF is a risk factor for worse outcomes in patients admitted with COVID19 in the ICU.