The heart is a destination for metastases of various types of primary tumors, with lung, breast, melanoma, and mesothelioma being the most common types. Recurrent isolated cardiac metastasis presenting as a cavitary mass is rare. We present a case of recurrent isolated cavitary metastatic mass to the right atrium in a patient with the history of breast cancer who presented with new-onset atrial fibrillation. The patient successfully received radiation therapy with the resolution of the mass confirmed on repeat echocardiography.