Thymic carcinoma is a rare, highly aggressive type of tumor that typically occurs in the anterior mediastinum. We describe the case of a 73-year-old man who presented with weakness, cough, dyspnea, anorexia, and weight loss. An echocardiogram showed an intrapericardial mass that occupied the space around the lateral walls of the left ventricle and distally compressed the right ventricle. Magnetic resonance imaging and a biopsy confirmed the presence of intrapericardial primary thymic carcinoma. The patient underwent surgical excision of the tumor and died of right ventricular rupture during the procedure. This case highlights the importance of considering thymic carcinoma whenever an otherwise unexplained intrapericardial mass is encountered.