Effect of atrial fibrillation (AF) on short- and long-term outcomes in heart failure (HF) is controversial. Accordingly, we examined this relationship in a national multicenter project using data from the Hearts Function Assessment Registry Trial in Saudi Arabia that studied the clinical features and outcomes of patients admitted with de novo and acute on chronic HF. Out of 2593 patients with HF, 449 (17.8%) had AF at presentation. Patients with AF were more likely to be males and older (mean age 65.2 ± 15.0 vs 60.5 ± 14.8 years) to have a history of ventricular tachycardia/ventricular fibrillation (3.1% vs 1.9%) or cerebrovascular accident (15.0% vs 8.5%). However, they were less likely to have diabetes (66.0% vs 55.9%) or coronary artery disease (55.6% vs 42.3%). The 1-, 2-, and 3-year crude mortality rates were significantly higher in patients with AF (23.2% vs 18.3%, 27.4% vs 22.3%, and 27.8% vs 23.2%, respectively). However, there was no significant difference in mortality after adjusting for covariates. Thus, in patients admitted with HF, AF upon presentation was not associated with increased mortality.