Aim To investigate the clinical features of heart failure in extremely elderly patients. Methods We analyzed 1163 consecutive hospitalized heart failure patients. The patients were divided into an extremely elderly group (≥85 years‐of‐age, n = 88) and a non‐extremely elderly group (<85 years‐of‐age, n = 1075). Results The extremely elderly group had higher rates of hypertension, chronic kidney disease, anemia, higher systolic blood pressure and lower body mass index, and lower use of β‐blockers and anticoagulants compared with the non‐extremely elderly group. During the mean follow‐up period of 1038 days, the extremely elderly group had higher mortality compared with the non‐extremely elderly group (P < 0.001). In multivariate analysis, in the non‐extremely elderly group, age (HR 1.027, P < 0.001), body mass index (HR 0.919, P < 0.001), New York Heart Association III or IV (HR 3.626, P < 0.001), preserved ejection fraction (HR 0.553, P < 0.001), anemia (HR 1.941, P < 0.001), β‐blockers (HR 0.695, P = 0.028) and renin–angiotensin system inhibitors (HR 0.603, P = 0.001) were independent predictors for all‐cause death. In contrast, atrial fibrillation (HR 2.042, P = 0.015) and renin–angiotensin system inhibitors (HR 0.470, P = 0.014) were independent predictors for all‐cause death in the extremely elderly group, suggesting that the prognostic factors were different between the two groups. Conclusions We should be careful of atrial fibrillation and renin–angiotensin system inhibitors in managing extremely elderly patients with heart failure. Geriatr Gerontol Int 2017; ••: ••–••.