BACKGROUND: Atrial fibrillation (AF) is associated with a higher incidence of stroke, heart failure, and mortality. Risk assessment of clinical outcomes in patients hospitalized acutely with AF remains a challenge. PURPOSE: To investigate if soluble urokinase plasminogen activator receptor (suPAR) levels at admission to the Emergency Department (ED) are associated with 1-year all-cause mortality in patients admitted with AF. METHODS: A prospective cohort study of patients consecutively admitted to the medical ED of a university hospital in Copenhagen, Denmark, between 2020 and 2022 with symptoms of COVID-19. Patients were included if they were admitted with AF as the primary or secondary diagnosis. All patients had suPAR measured at the index admission, and follow-up was up to 1 year. The association between suPAR and 1-year mortality was investigated with multivariate Cox regression. We adjusted for age, sex, smoking, C-reactive protein, creatinine, hemoglobin, albumin, and comorbidities. RESULTS: Of the 7,258 patients included during the period, 362 (5.0%) patients were admitted with AF as the primary or secondary diagnosis. Due to missing data, 23 (6.4%) patients were excluded. Among the remaining 339 patients, 68 (20.1%) patients were dead at follow-up. The multivariate Cox regression showed that elevated suPAR was independently associated with an increased risk of 1-year mortality, with a hazard ratio of 1.12 (95% confidence interval: 1.05-1.20,  < 0.001). CONCLUSION: Elevated suPAR levels were significantly associated with 1-year all-cause mortality in patients acutely admitted with AF to the ED.