Background Heart failure is a significant cause of morbidity and mortality, yet patient risk stratification may be difficult. Prevention or treatment of atrial fibrillation (AF) may be an important strategy in these patients that could positively affect their outcome. It has been demonstrated that in patients with systolic dysfunction, prolonged QRS duration (QRSd), an easily measured electrocardiographic parameter, is associated with AF. Hypothesis Prolonged QRSd is associated with an increase in prevalence of AF in patients with heart failure with preserved ejection fraction(HFPEF). Methods Between February 2006 and February 2009, 718 patients were discharged with a diagnosis of HF from the Dartmouth‐Hitchcock Medical Center. Of these, 206 had EF ≥50% by echocardiography performed within 72 hours of admission. After exclusions, 82 patients remained, of which 25 had AF and 57 had sinus rhythm. Characteristics of the AF and sinus‐rhythm patients were compared in this pilot study. Results After adjustment for age, prior diagnosis of HF, and left atrial area, there was a nonsignificant trend (odds ratio: 2.2, 95% CI of 0.3‐17.2) for a QRSd >120 ms to be associated with AF. Conclusions Similar to results in patients with systolic dysfunction, patients with preserved EF may have an association between a prolonged QRSd and AF.