Heart failure (HF) and atrial fibrillation (AF) often coexist. Subjects with permanent AF show the highest prevalence of HF. Patients with incident AF have HF in a great number of cases and, reciprocally, in patients with incident HF, an AF can be frequently found. The simultaneous presence of the two conditions is associated with mortality rates higher than those observed in individuals with only one or none of them. Interestingly, HF and AF could synergistically promote in elderly patients the development of disability and dementia. Inflammatory mechanisms coupled with changes of renin-angiotensin system, hormonal pathways and neuro-mediators could simultaneously promote left atrium remodeling and sustain both HF and AF. Beta-blockers and digoxin seem to have small therapeutic effect and limited influence on prognosis in these very complex patients. Sinus rhythm restoration could slow down the progression of disability in symptomatic subjects. Recent evidence seem to suggest that upstream therapy coupled with rehabilitation, and that AV node ablation associated with cardiac resynchronization therapy could benefit subjects with HF and AF. In conclusion, elderly patients simultaneously presenting problems of cardiac function and arrhythmia are an important challenge for geriatric medicine, and request important efforts to improve their functional profile and prognosis.