Aims: Heart failure (HF) with mid-range ejection fraction (HFmrEF) shares similar diagnostic criteria to HF with preserved ejection fraction (HFpEF). Whether left atrial (LA) function differs between HFmrEF and HFpEF is unknown. We, therefore, used 2D-speckle-tracking echocardiography (2D-STE) to assess LA phasic function in patients with HFpEF and HFmrEF. Methods and results: Consecutive outpatients diagnosed with HF according to current European recommendations were prospectively enrolled. There were 110 HFpEF and 61 HFmrEF patients with sinus rhythm, and 37 controls matched by age. LA phasic function was analysed using 2D-STE. Peak-atrial longitudinal strain (PALS), peak-atrial contraction strain (PACS), and PALS-PACS were measured reflecting LA reservoir, pump, and conduit function, respectively. Among HF groups, most of left ventricular (LV) diastolic function measures, and LA volume were similar. Both HF groups had abnormal LA phasic function compared with controls. HFmrEF patients had worse LA phasic function than HFpEF patients even among patients with LA enlargement. Among patients with normal LA size, LA reservoir, and pump function remained worse in HFmrEF. Differences in LA phasic function between HF groups remained significant after adjustment for confounders. Global PALS and PACS were inversely correlated with brain natriuretic peptide, LA volume, E/A, E/e', pulmonary artery systolic pressure, and diastolic dysfunction grade in both HF groups. Conclusion: LA phasic function was worse in HFmrEF patients compared with those with HFpEF regardless of LA size, and independent of potential confounders. These differences could be attributed to intrinsic LA myocardial dysfunction perhaps in relation to altered LV function.