We describe a patient with progressive cutaneous T-cell lymphoma (CTCL) and development of subacute cardiac failure. Symptomatic lymphomatous involvement of the heart may be more common in patients with CTCL than in other lymphomas because the former is more likely to be associated with circulating tumor cells and hematogenous spread to the myocardium. No single symptom or sign is highly predictive of cardiac involvement, but unexplained tachyarrhythmias, conduction disturbances, low voltage on ECG, and unexplained cardiac enlargement should arouse clinical suspicion. Although echocardiography may be helpful in suggesting cardiac involvement, endomyocardial biopsy should be considered in patients with a reasonable chance of responding to chemotherapy or radiation.