Chronic obstructive pulmonary disease (COPD) and cardiovascular disease often coexist, and acute cardiac events frequently occur during COPD exacerbations. Even when cardiac complications are not clinically apparent, biochemical evidence of cardiac dysfunction is often noted during exacerbations and portends poor prognosis. Diagnosis of cardiac disease in COPD can be difficult and necessitates a high degree of clinical suspicion. However, the additional strain of an exacerbation could be a pivotal moment, during which previously unsuspected cardiac dysfunction is exposed. In this Review, we present evidence about cardiac involvement in exacerbations of COPD, and discuss diagnostic challenges and treatment opportunities.