The prognostic impact of hospital-acquired pneumonia (HAP) in acute heart failure (AHF) patients have not been fully elucidated. We evaluated 776 consecutive hospitalized AHF patients. The primary in-hospital outcomes were all-cause death and worsening heart failure (WHF), while the outcome following discharge was all-cause death. The clinical diagnosis of HAP was based on clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Patients with HAP had a significantly higher incidence of in-hospital death (12% vs. 1%, p < 0.001), WHF during the hospitalization (28% vs. 7%, p < 0.001), and longer length of hospital stay (p = 0.003) than those without. Among patients who survived at discharge, during a median follow-up period of 741 (interquartile range 422-1000) days, the incidence of all-cause death was significantly higher in patients with HAP than in those without (p < 0.001). In the multivariable Cox regression, HAP development was independently associated with all-cause death after discharge (HR [hazard ratio] 1.86, 95%CI [confidence interval] 1.08-3.19). Furthermore, older age (OR [odds ratio] 1.04, 95%CI 1.01-1.08), male sex (OR 2.21, 95%CI 1.14-4.28), and higher serum white blood cell count (OR 1.18, 95%CI 1.09-1.29) and serum C-reactive protein (OR 1.08, 95%CI 1.01-1.06) were independently associated with HAP development. In hospitalized patients with AHF, HAP development was associated with worse clinical outcomes, suggesting the importance of prevention and early screening for HAP.