Background: Some 20% of patients with stable Chronic Obstructive Pulmonary Disease (COPD) might have heart failure (HF). HF contribution to acute exacerbations of COPD (AECOPD) presenting to the emergency department (ED) is not well established. Aims: To assess (1) the HF incidence in patients presenting to the ED with AECOPD; (2) the concordance between ED and respiratory ward (RW) diagnosis; (3) the factors associated with risk of death after hospital discharge. Methods: Retrospective chart review of 119 COPD patients presenting to ED for acute exacerbation of respiratory symptoms and then admitted to RW where a final diagnosis of AECOPD, AECOPD and HF and AECOPD and OD (other diagnosis), was obtained. ED and RW diagnosis were then compared. Factors affecting survival at follow-up were investigated. Results: At RW, 40.3% of cases were diagnosed of AECOPD, 40.3% of AECOPD and HF and 19.4% of AECOPD and OD, with ED diagnosis coinciding with RW’s in 67%, 23%, and 57% of cases respectively. At RW, 60% of patients in GOLD1 had HF, of which 43% were diagnosed at ED, while 40% in GOLD4 had HF that was never diagnosed at ED. Lack of inclusion in a COPD care program, HF, and early readmission for AECOPD were associated with mortality. Conclusions: HF is highly prevalent and difficult to diagnose in patients in all GOLD stages presenting to the ED with severe AECOPD, and along with lack of inclusion in a COPD care program, confers a high risk for mortality.