Objective Most patients with atrial fibrillation (AF) have risk factors and coexisting conditions that increase their mortality risk. We performed a cause-of-death analysis to identify predictors of mortality in hospitalised patients with AF in France. Methods and results In this retrospective, population-based cross-sectional study, the Programme de médicalisation des systèmes d'information was used to identify 533 044 adults with a diagnosis of AF or atrial flutter hospitalised for any reason in France from January through December 2012. Stepwise multivariable analyses were performed to identify determinants of mortality. The mean age was 78.0±11.4 years, 47.1% were women, and the mean CHA2DS2-VASc score was 4.0±1.8. During hospitalisation, 9.4% (n=50 165) of the patients died, 34% due to a cardiovascular event, most often heart failure (16.6%), stroke/transient ischaemic attack/systemic embolism (9.8%) or vascular or ischaemic disease (4.0%). The strongest predictors of overall death were age ≥75 years (OR 2.57, 95% CI 2.47 to 2.68), renal failure (OR 1.85, 95% CI 1.81 to 1.89), cancer (OR 1.81, 95% CI 1.78 to 1.85) and lung disease (OR 1.58, 95% CI 1.55 to 1.62). Conclusions Cardiovascular events were the most common cause of death, occurring in one-third of patients, in this comprehensive study of hospitalised patients with AF. Despite the high risk of stroke in this population, only 10% died from stroke/transient ischaemic attack/systemic embolism. The strongest predictors of overall death were non-cardiovascular. Physicians should be encouraged to focus on preventable serious and disabling cardiovascular events (such as stroke) as well as on potentially fatal non-cardiovascular comorbidities.