Left ventricular (LV) diastolic dysfunction plays a crucial role in heart failure with reduced ejection fraction (HFrEF). LV stiffness is a main component of diastolic function, but its role and prognostic value in HFrEF patients remains unclear. This study aimed to determine whether diastolic wall strain (DWS) as a noninvasive and simple marker of LV stiffness can predict the prognosis of HFrEF patients who were administrated chronic beta blockade enough. We enrolled 75 HFrEF patients who were administrated chronic beta blockade. We evaluated the echocardiographic parameters and plasma brain natriuretic peptide (BNP) before the induction of beta blockade and also obtained pulmonary artery wedge pressure (PAWP) from the right heart catheterization. DWS was obtained from standard M-mode echocardiography as follows: DWS = [(LV posterior wall thickness (LVPWT) at end-systole − LVPWT at end-diastole)/LVPWT] at end-systole. DWS did not correlate with other echocardiographic parameters and PAWP. We defined primary outcome as HF hospitalization or cardiovascular death and followed for 7 years. The incidence rate was higher in low DWS than high DWS patients (p = 0.04). Other echocardiographic parameters could not be significant predictors of HFrEF outcome under the condition of enough beta blocker therapy. In multivariate analysis, DWS was the independent contributor to the event-free time. Impaired LV stiffness evaluated with DWS was associated with worse outcome and DWS might be an independent prognostic factor in HFrEF patients with chronic beta blockade.