The efficacy of beta (β) blockers in critically ill patients with congestive heart failure (CHF) remains uncertain. This study investigated the association of β blockers use with 1-year all-cause mortality in these patients. Utilizing a retrospective cohort, the Medical Information Mart in Intensive Care-Ⅳ database, we identified critically ill CHF patients between 2008 and 2022. Stratified by β blockers use, Kaplan-Meier survival analysis and Cox models examined the association. Subgroup analyses investigated its effect across various patient characteristics. It comprised 13,908 eligible patients, of whom 74.3% received β blockers. β blockers use was associated with a reduction in mortality (HR: 0.51, 95% CI: 0.49-0.54, p < 0.001). Subgroup analyses revealed more benefits in non-elderly, male, hypertensive, diabetic or sepsis patients, as well as those undergoing mechanical ventilation or continuous renal replacement therapy (CRRT). Patients with elevated baseline heart rates or reduced left ventricular ejection fraction (LVEF) experienced greater benefits (p for interaction < 0.001). Additionally, selective β1 blockers offered superior survival benefits than non-selective β blockers in patients with LVEF of 50% or higher, and these benefits were pronounced in those with elevated baseline white blood cell counts (p for interaction = 0.022). The use of β blockers was linked to a reduction of all-cause mortality in critically ill patients with CHF, particularly in subgroups characterized by younger age, male gender, hypertension, diabetes, sepsis, undergoing CRRT or mechanical ventilation, and those exhibiting elevated baseline heart rates or reduced LVEF. These findings are potentially influenced by unmeasured confounders and need to be confirmed by prospective randomized controlled trials.