Hydatid cyst, a human parasitic disease, remains a clinical problem in undeveloped and developing countries. Although liver and lungs are regular sites of infection, rarely other organs such as the heart can be involved. Herein, we report an isolated cardiac hydatid cyst in an 87-year-old man. He had a history of dementia for 5 years and no history for cardiac or pulmonary disease. He presented with exertional dyspnoea which continued up to 6 months. The diagnosis was made by echocardiography and computed tomography (CT). The patient was inoperable and was treated with albendazole 10 mg/kg for 6 months. After a 6-month follow-up, echocardiography revealed reduction in the size of the cyst. We believe this is the first documented case of cardiac hydatid cyst which regressed with only medical treatment in an older adult with dementia.