We present asymptomatic right atrial myxoma in a patient with breast ductal adenocarcinoma. A 58-year-old female was referred to our clinic for the evaluation of the potential cardiotoxic side effects of anthracycline-based chemotherapy. She had a 10-month history of modified radical mastectomy for ductal adenocarcinoma of the breast, followed by adjuvant chemotherapy. To evaluate potential side effects of anthracycline-based regimen, transthoracic echocardiography was performed, which showed a highly mobile, cystic, and heterogeneous mass, 20 x 25 mm in size, located in the right atrium. Transesophageal echocardiography confirmed the highly mobile mass originating from the inferior vena cava and extending to the right atrium. Surgery was planned. Upon exposure, the tumor had a broad base, with attachment to the lower dorsal free wall, interatrial septum of the right atrial cavity, and upper border of the inferior vena cava. The tumor was completely excised and histopathologic diagnosis was myxoma. Localization of right atrial myxoma at the junction of the inferior vena cava and right atrium is a rare condition, and its coexistence with breast carcinoma has only been reported once.