Beta-blockers (BB) drugs have been used for decades worldwide, mainly to treat hypertension. However, in recent epidemiological studies, BBs were suggested to improve cancer prognosis. In the wake of this evidence, we evaluated the possible therapeutic effect of BBs in triple-negative breast cancer (TNBC) patients. We identified 800 postmenopausal women operated between 1997 and 2008 for early primary TNBC. The effect of BB intake on the risk of breast cancer (BC) recurrence and death was evaluated through competing risk and Cox regression survival models. At cancer diagnosis, 74 (9.3 %) women out of 800 were BBs users. Median age was 62 years in BB users and 59 years in non-users (P = 0.02). BB users and non-users were similarly distributed by all tumor characteristics. The 5-year cumulative incidence of BC-related events was 13.6 % in BB users and 27.9 % in non-users (P = 0.02). The beneficial impact of BBs remained statistically significant at multivariable analysis (HR, 0.52; 95 % CI 0.28-0.97), after the adjustment for age, tumor stage, and treatment, peritumoral vascular invasion and use of other antihypertensive drugs, antithrombotics, and statins. Adjusted HRs for metastases and for BC deaths were 0.32 (95 % CI 0.12-0.90) and 0.42 (95 % CI 0.18-0.97), respectively, in favor of BBs. Hypertension, other antihypertensive drugs, antithrombotics, and statins did not impact prognosis. In this series of postmenopausal TNBC patients, BB intake was associated with a significantly decreased risk of BC-related recurrence, metastasis, and BC death. Innovative therapeutic strategies including BBs should be urgently explored in cancer patients.