To assess the clinical effectiveness of beta-blocker therapy in individuals with heart failure (HF) and chronic lung disease and of angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin II receptor blockers (ARBs) in individuals with HF and chronic kidney disease. Retrospective cohort study. Community. Individuals with HF with reduced ejection fraction (HFrEF) or HF with preserved ejection fraction (HFpEF). We undertook separate new-user cohort studies to assess the effectiveness of beta-blocker therapy in treating HF and chronic lung disease and ACE-Is and ARBs in treating HF and chronic kidney disease (CKD). Individuals with a chronic lung disease diagnosis were included in the group with HF and chronic lung disease (International Classification of Diseases, Ninth Revision, codes 490-496, 518). Individuals with an estimated glomerular filtration rate less than 60 mL/min per 1.73 m2 were included in the group with HF and CKD. The clinical outcomes of interest were death from any cause, hospitalization for HF, and hospitalization for any reason. We fitted pooled logistic marginal structural models using inverse probability weighting, stratified according to HF type. For individuals with HFrEF with chronic lung disease, beta-blocker therapy was protective against death (relative risk (RR) = 0.58, 95% confidence interval (CI) = 0.44-0.77) and hospitalization for HF (RR = 0.78, 95% CI = 0.60-1.00). For those with HFpEF, no statistically significant associations between beta-blocker therapy use and any of the outcomes were observed. We found ACE-I and ARB use to be protective against all three outcomes of interest in individuals with HFrEF (death from any cause: RR = 0.60, 95% 0.40-0.91; hospitalization for HF: RR = 0.43, 95% CI = 0.28-0.67; hospitalization for any reason: RR = 0.63, 95% CI = 0.45-0.89, respectively) and those with HFpEF (death from any cause: RR = 0.52, 95% CI = 0.33-0.81; hospitalization for HF: RR = 0.35, 95% CI = 0.18-0.68; hospitalization for any reason: RR = 0.67, 95% CI = 0.47-0.95). Large observational studies may allow for identification of important subgroups of individuals with HF that might benefit from existing treatment approaches. Our findings may also better inform the design of more-definitive future observational studies and randomized trials.