Metastases to the heart and pericardium are much more common than primary malignant neoplasms. Primary malignant pericardial mesothelioma is a rare tumor that arises from the mesothelial cells of the pericardium. It is usually characterized by a delayed diagnosis, a low response to treatment, and a poor prognosis with an overall survival up to six months after the onset of symptoms. We report a rare case of a 32-year-old woman with primary pericardial malignant mesothelioma that was diagnosed 4 months after the onset of pericardial effusion as the first clinical manifestation.