Background Atrial fibrillation (AF) and heart failure (HF) often co-exist and are closely intertwined, each condition worsening the other. The temporal relationships between these two disorders have not yet been fully explored. We aimed to address the outcomes of patients hospitalized with HF and AF based on the chronology of the onset of the two disorders. Methods From the administrative database for the whole French population, we identified 1,349,638 patients diagnosed with both AF and HF between 2010 and 2018; 956,086 of these AF patients developed HF first (prevalent HF), and 393,552 developed HF after AF (incident HF). The outcome analysis (all-cause death, cardiovascular (CV) death, ischemic stroke or hospitalization for HF) was performed with follow-up starting at the time of last event between AF or HF in the whole cohort and in 427,848 propensity score-matched patients. Results During follow-up (mean follow-up 1.6 ± 1.9 year), matched patients with prevalent HF had a higher risk of all-cause death (21.6 vs. 19.3%/year, hazard ratio (HR) 1.10, 95% CI 1.08–1.11), CV death (7.7 vs. 6.5%/year, HR 1.14, 95% CI 1.12–1.16) as well as re-hospitalization for HF (19.4 vs. 13.2%/year, HR 1.44, 95% CI 1.41–1.46) than those with incident HF. The risk for ischemic stroke was lower in prevalent HF than in incident HF (1.2 vs. 2.4%/year, HR 0.50, 95% CI 0.48–0.52). Conclusions We identified two distinct clinical entities: patients in whom HF preceded AF (prevalent HF) had higher mortality and higher risk of re-hospitalization for HF.