Background: The number of patients requiring dialysis is increasing worldwide, and the atrial fibrillation (AF) prevalence among hemodialysis (HD) patients is higher than in the general population. There have been no studies of Korean AF patients undergoing HD investigating how AF affects outcomes, for example, in terms of all-cause mortality, hospitalization, and stroke events. We conducted a large-scale retrospective cohort study with data from the National Health Insurance System (NHIS) to determine how AF affects these outcomes. Methods: In 2013, the Health Insurance Review and Assessment (HIRA) service, a Korean national health insurance scheme, collected data from 21,839 HD patients for evaluating the adequacy of dialysis centers. All-cause mortality, hospitalization, and stroke events were compared between patients with and without AF. Sub-analyses compared these outcomes between patients receiving and not receiving warfarin. Results: Cox regression analysis found that AF was a significant risk factor for death from any cause (HR, 1.356; 95% CI, 1.222-1.506, P < 0.001), hospitalization (HR, 1.323; 95% CI, 1.225-1.430, P < 0.001), and hemorrhagic stroke (HR, 1.500; 95% CI, 1.050-2.141, P = 0.026). AF was not significantly associated with an increased risk of ischemic stroke. The use of warfarin was significantly associated with hemorrhagic stroke incidence (HR, 1.593; 95% CI, 1.075-2.360, P = 0.020), while there was no significant correlation between warfarin treatment and all-cause mortality, hospitalization, and ischemic stroke. Conclusions: This cohort study of Korean dialysis patients showed that AF was a risk factor for multiple outcomes among HD patients.