The relationship between the short-term prognosis of acute heart failure (AHF) and acute kidney injury (AKI) using the risk, injury, failure, and end stage (RIFLE) criteria has already been reported, however, the relationship between the long-term prognosis and AKI has not. We investigated the relationship between the long-term prognosis after discharge and AKI using the RIFLE criteria. Five hundred patients with AHF admitted to our intensive care unit were analyzed. Patients were assigned to a no AKI (n = 156), Class R (risk; n = 201), Class I (injury; n = 73), or Class F (failure; n = 70) using the most severe RIFLE classifications during hospitalization. We evaluated the relationships between the RIFLE classifications and any-cause death, and HF events including death and readmission for HF within 1 year. A multivariate logistic regression model found that Class I (P = 0.013, OR: 2.768; 95% CI: 1.236-6.199) and Class F (P < 0.001, OR: 7.920; 95% CI: 3.497-17.938) were independently associated with any-cause death, and Class F was associated with HF events (P = 0.001, OR: 3.486; 95% CI: 1.669-7.281). The Kaplan-Meier survival curves showed the prognosis, including death, to be significantly poorer in Class I than in no AKI and Class R, to be significantly poorer in Class F than in no AKI, Class R, and Class I, and the prognosis including HF events to be significantly poorer in Class F than in no AKI, Class R, and Class I. The presence of severe AKI (Class I and F) was independently associated with long-term mortality for AHF.