Hydatid disease is a rare parasitic disease, which mainly involves liver then lung tissues. Cardiac involvement is very rare, especially when there is not hepatic involvement. We describe a 47-year-old woman with a history of a lung hydatid cyst who was referred to Rajaei Heart Center, Tehran, Iran in 2012. Her chest computed tomographic scan showed a cardiac mass. Echocardiographic examination illustrated a large, well-defined heterogeneous mass (4.5 × 2.5 cm) in the roof of the right atrium with attachment to the crista terminalis without compressive effect on the inferior and superior venae cavae. The patient was candidate for open-heart surgery via median sternotomy. A cystic mass was observed in the lateral aspect of the right atrial wall. After an injection of hypertonic normal saline into the cystic lesion, the mass was excised totally. The right atrial defect was reconstructed with autologous pericardium. The patient was discharged from the hospital in good condition. Histological examination confirmed the diagnosis of the hydatid cyst.