Abstract Background Recent clinical trials have demonstrated the potential efficacy and safety of angiotensin receptor-neprilysin inhibitors (ARNI) in patients with heart failure (HF) with mildly reduced or preserved ejection fraction. Nevertheless, the generalizability of these findings in real-world clinical settings remains to be determined. We aimed to compare the real-world effectiveness of ARNI versus angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACEI/ARB)on clinical outcomes in HF patients with mildly reduced or preserved ejection fraction. Methods Patient-level data was derived from the China Cardiovascular Association Database-HF Center Registry. We included exclusively a subpopulation of HF patients with left ventricular ejection fraction (LVEF) >40% and comorbid with hypertension. Patients prescripted with ARNI at discharge and sustaining to ARNI therapy during follow-up were categorized as the ARNI group, while those maintaining the usage of ACEI/ARB after discharge were designated as the ACEI/ARB group. In complete cases, the primary endpoint of all-cause mortality at one year was assessed by the 1:1 propensity score matching (PSM) method. Results In all HF patients with LVEF >40% comorbid with hypertension, the usage of ARNI has increased from 0.9% in 2017 to 37.2% in 2021. A total of 3348 patients in the ARNI group and 7688 patients in the ACEI/ARB group were identified for comparative effectiveness. After 1:1 PSM, 5482 patients were included in the primary analysis, with 2741 patients in each treatment arm. The proportion of patients receiving higher dosages of ARNI (200mg/d and 400mg/d) was 20.9%, 26.6%, 29.2%, and 30.3% at discharge, 1-month, 3-month, and 1-year, respectively. Over the 1-year follow-up, ARNI was associated with a 20% relative reduction in all-cause death compared to the ACEI/ARB therapy (10.5% vs. 12.9%, adjusted hazard ratio [HR], 0.80 [95% CI, 0.69-0.94], P=0.005). The absolute risk difference in all-cause death between ARNI and ACEI/ARB arms was 2.88 per 100 patient-years (incidence rate difference, -2.88 [95% CI, -4.86 to -0.9]). Cardiovascular death also tended to decrease in the ARNI group but with missed statistical significance (4.5% vs. 4.9%, adjusted HR, 0.89 [95% CI, 0.70-1.14], P=0.373). Treatment benefits were more significant in those with LVEF between 40-50% (adjusted HR, 0.62 [95% CI, 0.48-0.79]), 50-60% (adjusted HR, 0.85 [95% CI, 0.68-1.06]), but not observed in HF patients with LVEF>60% (adjusted HR, 1.80 [95% CI, 1.08-2.98]; Pinteraction<0.001). Conclusion In real-world clinical settings, treatment with ARNI was associated with a significant relative risk reduction in all-cause mortality compared with ACEI/ARB in HF patients with mildly reduced or preserved LVEF. The cardiovascular benefit was concentrated in patients with LVEF ≤60%.