Background: Symptomatic pulmonary embolism (PE) is a major cause of cardiovascular death and morbidity. Estimated prevalence and incidence of atrial fibrillation (AF) in developed countries are between 388-661 per 100,000, and 90-123 per 100,000 person-years respectively. However, the prevalence and incidence of AF in patients presenting with an acute PE and its predictors are not clear. Methods: Individual patient clinical details were retrieved from a database containing all confirmed acute PE presentations to a tertiary institution from 2001-2012. Prevalence and incidence of AF was tracked from a population registry by systematically searching for AF during any hospital admission (2000-2013) based on International Classification of Disease (ICD-10) code. Results: Of the 1,142 patients included in this study, 935 (81.9%) had no AF during index PE admission whilst 207 patients had documented baseline AF (prevalence rate 18,126 per 100,000; age-adjusted 4,672 per 100,000). Of the 935 patients without AF, 126 developed AF post- PE (incidence rate 2,778 per 100,000 person-years; age-adjusted 984 per 100,000 person-years). Mean time from PE to subsequent AF was 3.4 ± 2.9 years. Total mortality (mean follow- up 5.0 ± 3.7 years) was 42% (n = 478): 35% (n = 283), 59% (n = 119) and 60% (n = 76) in the no AF, baseline AF and subsequent AF cohorts respectively. Independent predictors for subsequent AF after acute PE include age (hazard ratio [HR] 1.06, 95% confidence interval [CI] 1.04-1.08, p<0.001), history of congestive cardiac failure (HR 1.88, 95% CI 1.12- 3.16, p = 0.02), diabetes (HR 1.72, 95% CI 1.07-2.77, p = 0.02), obstructive sleep apnea (HR 4.83, 1.48-15.8, p = 0.009) and day-1 serum sodium level during index PE admission (HR 0.94, 95% CI 0.90-0.98, p = 0.002). Conclusions: Patients presenting with acute PE have a markedly increased age-adjusted prevalence and subsequent incidence of AF. Screening for AF may be of importance post-PE.