Introduction: Heart failure is an important leading cause of mortality and morbidity despite optimal medical treatment and device therapy. Sacubitril/valsartan, a first-generation drug, was approved to use heart failure treatment recently. There are limited studies on the relationship between sacubitril/valsartan and left ventricu- lar contraction. In our study, we aimed to evaluate the changes in left ventricular ejection fraction (LVEF) after sacubitril/valsartan treatment. Patients and Methods: Fifty-two patients with heart failure and reduced ejection fraction (HFrEF) were en- rolled in this study. The baseline demographic, clinical, and echocardiographic characteristics of 52 patients were compared using the Bayesian method. Results: Fifty-two patients with heart failure and reduced ejection fraction (HFrEF) were included in the final analysis (66.2 ± 9.3 years, 69.2% male). Sacubitril/valsartan initial dose was low in 44.2% of patients, and intermediate in 55.8%. In the low initial dose population, the increase in absolute LVEF was 3.87 (95% HDI 1.53-6.20) and in the intermediate initial dose population, the increase in absolute LVEF was 5.89 (95% HDI 4.18-7.61). In the female population, the increase in absolute LVEF was 5.56 (95% HDI 3.49-7.63) and in the male population 4.75 (95% HDI 2.91-6.58) respectively. Conclusion: In this study, we demonstrated that sacubitril/valsartan is associated with increased LVEF re- gardless of baseline clinical characteristics.