Cardiac sarcomas are the predominant type of malignant primary cardiac tumors, especially in cases where the patients are <50 years of age and have a poor prognosis, with a 5-year survival rate of less than 15%. Cardiac angiosarcomas are a common type of cardiac sarcoma. Cardiac angiosarcoma is a highly aggressive tumour, with approximately 75% of the cases originating in the right atrium, and has a higher incidence in males than in females. The present case report describes a 31-year-old woman who was initially suspected of having tuberculous pericarditis and was treated with anti-tuberculous medication. However, cardiac imaging analysis revealed a right atrial pseudoaneurysm with spontaneous rupture of the lateral right atrium. The patient underwent surgical exploration, in which a large mass infiltrating the right atrium, right ventricle, and right pleura with the ruptured right atrium was discovered. Mass excision and right atrial repair were performed, and the patient was admitted to the intensive care unit; however, she subsequently succumbed to her illness. Histopathological examination confirmed the diagnosis of cardiac angiosarcoma. Primary cardiac angiosarcoma is a rare and aggressive tumor that is difficult to diagnose. Most patients have systemic metastasis and a poor prognosis at the time of presentation. A confirmatory diagnosis was made after sample collection, highlighting the need to improve diagnostic and therapeutic methods for this disease.