Left atrial dysfunction is associated with exercise intolerance and poor prognosis in heart failure (HF). The effects of exercise training on atrial function in patients with HF with mid-range ejection fraction (HFmrEF) are unknown. The purpose of the present study was to assess the effects of a 12-weeks supervised concurrent, aerobic continuous plus resistance, exercise training (SCT) pro-gram on left atrial function of patients with HFmrEF. The study included 70 stable patients, who were randomly assigned into two groups: SCT with (three session/week) or a control (CON) group directed to follow contemporary exercise preventive guidelines at home. Before starting the training program and at 12-weeks, all patients performed: ergometric test, 6-minute walk test and echocardiography. At 12-weeks, exercise duration at ergometric test and distance walked at 6-minute walk test presented a significant greater increase in the SCT compared to control (be-tween-groups p 0.0001 and p 0.004 respectively). Peak atrial longitudinal strain and conduit strain presented an increase of 29% and 34% respectively in the SCT and were unchanged in the CON (between-groups p 0.008 and p 0.001 respectively). Peak atrial contraction strain increased of 21% in the SCT with no changes in the CON (between-groups p 0.002). Left ventricular global longi-tudinal strain increased significantly SCT compared to control (between-groups p 0.03). In con-clusions SCT improved left atrial and left ventricular function in HFmrEF