AimsThe prognostic significance of N‐terminal pro B‐type natriuretic peptide (NT‐proBNP) in heart failure with preserved ejection fraction (HFpEF) has been well established. HFpEF and atrial fibrillation (AF) commonly coexist, and each contributes to poor outcomes independently. Nevertheless, the ability of NT‐proBNP to predict AF in HFpEF patients remains uncertain.Methods and resultsA total of 367 HFpEF patients without baseline AF from the Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist (TOPCAT) trial were included. The Cox proportional hazard model was used to assess the association of NT‐proBNP with the risk of AF. The C‐statistic, categorical net reclassification index (NRI), and integrated discrimination improvement (IDI) were used to evaluate the ability of NT‐proBNP in new‐onset AF prediction. During a median follow‐up of 2.91 years, 17 (4.63%) new‐onset AF cases occurred. Every 1000 pg/mL increase in NT‐proBNP was associated with a 16% increase in the risk of AF occurrence after adjustments (hazard ratio, 1.16 [95% CI, 1.02–1.32]). NT‐proBNP showed a moderate performance for new‐onset AF at 3 years (C‐statistic, 0.67). Adding NT‐proBNP to CHADS2/R2CHADS2/CHA2DS2‐VASc/C2HSET scores improved their predictive performance for AF risk (CHADS2: C‐statistic, 0.63, CHADS2+NT: C‐statistic, 0.69, NRI, 47.46%, IDI, 1.18%; R2CHADS2: C‐statistic, 0.65, R2CHADS2+NT: C‐statistic, 0.70, NRI, 48.03%, IDI, 0.51%; CHA2DS2‐VASc: C‐statistic, 0.67, CHA2DS2‐VASc+NT: C‐statistic, 0.72, NRI, 49.41%, IDI, 0.86%; C2HSET: C‐statistic, 0.77, C2HSET+NT: C‐statistic, 0.80, NRI, 50.32%, IDI, 1.58%).ConclusionsAmong patients with HFpEF, the NT‐proBNP level was positively associated with the incidence of new‐onset AF and may be a promising predictor.