Aims: Identifying clinical and echocardiographic parameters associated with improvement in systolic function in outpatients with heart failure with reduced ejection fraction (HFrEF) could lead to more targeted treatment improving systolic function and outcome. Methods: In a retrospective cohort study, echocardiographic examinations from the first and final visit of 686 patients with HFrEF at the heart failure clinic at Gentofte Hospital were retrieved and analysed. Parameters associated with left ventricular ejection fraction (LVEF) improvement and survival according to LVEF improvement were assessed using linear regression and Cox regression, respectively. Beta-coefficients (β-coef) are standardised. Strain values are absolute. Results: While undergoing heart failure treatment, 559 (81.5%) patients improved systolic function ( "LVEF >0%), with 100 (14.6%) being super responders defined by LVEF improvement >20%. After multivariable adjustment, LVEF improvement was significantly associated with a less impaired global longitudinal strain (β-coef 0.25, p<0.001), higher tricuspid annular plane systolic excursion (β-coef 0.09, p=0.018), smaller left ventricular internal dimension in diastole (β-coef -0.15, p=0.011), lower E-wave/A-wave ratio (β-coef -0.13, p=0.003), higher heart rate (β-coef 0.18, p<0.001) and absence of ischaemic cardiomyopathy (β-coef -0.11, p=0.010) and diabetes (β-coef -0.081, p=0.033) at baseline. Mortality incidence rates differed with LVEF improvement ( "LVEF <0% vs "LVEF >0%, 8.3 vs 4.3 per 100 person years, p=0.012). Greater improvement in LVEF was associated with significantly lower mortality risk (tertile 1 vs tertile 3, HR 3.23, 95% CI 1.39 to 7.51, p=0.006). Conclusion: In this outpatient HFrEF cohort, most patients improved systolic function. Heart failure aetiology, comorbidities and echocardiographic measures of heart structure and function were significantly, independently associated with future LVEF improvement. Greater LVEF improvement was significantly associated with lower mortality.