Background: Chronic Lymphocytic Leukemia (CLL) is adults' most prevalent chronic leukemia. There is an increased report of cardiovascular comorbidities in these patients due to the multi-systemic impact of both the insidious disease and the associated side effects of its treatment. This study aimed to provide real-world contemporary data on the in-hospital outcomes among patients admitted for CLL with comorbid Congestive Heart Failure (CHF) in the United States. Methods: The study is a retrospective study that used the National Inpatient Sample database. We identified patients hospitalized for CLL from 2018-2020 and stratified them into two cohorts – with CHF and without CHF. Inclusion criteria include age ≥ 18 years and hospitalization primarily for active CLL. We excluded patients with aortic stenosis and those whose CLL were in remission. Inferential statistics - chi-squared test and Student t-test (as applicable) - was done on extracted data. The odds ratio was calculated using univariate and multivariate analyses. All analyses were done at a 95% confidence interval with a 2-tailed p-value <0.05 set as the cut-off for statistical significance. Results: A total of 210,012 hospitalizations of CLL were identified, of which 27.5% (57,650) had comorbid CHF. On univariate logistics regression analysis, the average length of hospitalization was statistically (p<0.001) prolonged by one day, and the cost of hospitalization increased by 9,640 + 1482 US dollars among those with CHF and active CLL. The odds of all-cause in-hospital mortality increased by 1.6 folds in these patients (P<0.001). However, after adjusting for individual patients and hospital-level cofounders, active CLL did not have a significant clinical impact on the duration and total cost of heart failure hospitalization. Active CLL, however, significantly increased the risk of all-cause in-hospital mortality by 1.3 folds (4.7% vs 7.2%; adjusted odds ratio 1.31, 95% CI 1.17-1.46; p<0.01) in patients with heart failure. Conclusions: Patients hospitalized for active CLL with a comorbid diagnosis of CHF have increased odds of in-hospital mortality compared to those without comorbid heart failure. This finding suggests the need for integrative multi-disciplinary care for CLL patients with comorbid CHF, such as cardio-oncology.