We report here an unusual case of pericardial tuberculoma that was misdiagnosed as thymic carcinoma on an imaging study. A 48-year-old woman was referred for evaluation of an anterior mediastinal mass. Computed tomography (CT) scans of the chest displayed cystic masses mimicking thymic carcinoma at the anterior mediastinum. Pericardiotomy and surgical drainage of the cystic masses were done, and pathologic examination of the excised pericardial specimen showed a chronic granulomatous inflammation with necrosis, compatible with tuberculosis. Acid-fast bacilli were also identified in the specimen. After treatment with anti-tuberculosis drugs and steroids, the patient showed clinical improvement. Although tuberculous pericarditis usually presents as pericardial effusion or constrictive pericarditis, it can also present as a pericardial mass mimicking thymic carcinoma on CT. Therefore, we suggest that tuberculous pericardial abscess should be included in the differential diagnosis of a mediastinal mass in Korea, with intermediate tuberculosis prevalence.