Clinical practice guidelines emphasize that optimal pharmacotherapy, including beta-blockers (BB), is a prerequisite before receiving cardiac resynchronization therapy (CRT) in eligible patients with heart failure (HF). However, the optimal dose of BB before CRT implantation cannot be tolerated in a number of patients. Sixty-three consecutive patients who underwent CRT in 2006–2013 were retrospectively investigated. Before receiving CRT, BB could not be introduced in 20 patients (32 %); the daily carvedilol-equivalent dose in other 43 patients was 5.6 ± 7.0 mg because of significant HF and bradycardia. After receiving CRT, BB could be introduced in almost all patients (n = 61, 97 %), and the daily BB dose increased from 5.6 ± 7.0 to 13.2 ± 7.8 mg (P < 0.001). Multivariate analysis indicated that the change of BB dose after CRT was independently associated with improved left ventricular end-systolic volume (LVESV) [β = −0.36; 95 % confidence interval (CI) −2.13 to −0.45; P < 0.01] after 6-months follow-up. Furthermore, Cox proportional hazard analysis also showed that the change in the BB dose (hazard ratio, 0.92; 95 % CI, 0.87–0.98; P < 0.01) as well as the New York Heart Association functional classification was an independent predictor of cardiac events. After initiating CRT, BB therapy can be introduced and up-titrated in intolerant HF patients. The up-titrated dose of BB after CRT was an independent predictor for the improvement of LVESV and HF prognosis.