A long-acting loop diuretic, azosemide, has been shown to improve long-term prognosis in patients with heart failure compared with a short-acting loop diuretic, furosemide. However, the therapeutic advantages of azosemide over furosemide have not been clearly established. In this study, we retrospectively analyzed clinical outcomes and laboratory data in patients with congestive heart failure treated with furosemide or azosemide, and the efficacy of these agents was compared. First, we screened 1900 patients and selected 124 (furosemide group: n = 40; azosemide group: n = 84) as the total study population. From these patients, we next selected 72 patients for the propensity score-matched analysis (furosemide group: n = 36; azosemide group: n = 36). The incidence of all-cause death and rehospitalization due to worsening heart failure during 24 months of follow-up was similar between the furosemide and azosemide groups in both the total study population and the propensity score-matched population. However, in the propensity score-matched analysis, the estimated glomerular filtration rate time-dependently decreased during 36 months of follow-up in the furosemide group (56.5 ± 19.5-43.2 ± 16.3 mL/min/1.73 m), whereas it did not change in the azosemide group (58.6 ± 22.0-50.3 ± 17.8 mL/min/1.73 m) (P = 0.032). Azosemide might have some potential advantage for renal protection over furosemide in patients with congestive heart failure.