Background: Left atrial (LA) volume is an important marker of cardiac dysfunction and cardiovascular outcome in heart failure (HF), but LA function is rarely measured. Methods: Left atrial emptying function (LAEF), its clinical associations and prognostic value was studied in outpatients referred with suspected HF who were in sinus rhythm and had cardiac magnetic resonance imaging (CMRI). Heart failure was defined as relevant symptoms and signs with either a left ventricular ejection fraction (LVEF) 400 pg/mL (or >125 pg/mL if taking loop diuretics). Results: Of 982 patients, 664 fulfilled the HF criteria and were in sinus rhythm. The median (interquartile range, IQR) LAEF was 42 (31–51)% and 55 (48–61)% in patients with and without HF (P