We report an extremely rare case of multifocal fibrosclerosis (MFS) with intracardiac solid masses. A 70-year-old woman with Hashimoto's disease had pericardial thickening and intracardiac masses. Histology of pericardiectomy showed only fibrosis. The clinical diagnosis was constrictive pericarditis. She died of postoperative infectious mediastinitis and cerebral infarction. Postmortem examination revealed intracardiac solid masses contiguous to thickened pericardium. Multifocal areas of fibrosis were also seen in the pericardium, mediastinum, abdominal cavity, and the retroperitoneum. The intracardiac masses and the areas of fibrosis were composed of collagenous fibers with various intensities of inflammatory infiltrates and sclerotic changes. Neoplastic changes were not observed. These histological features were similar to that of MFS. The intracardiac masses are interpreted as one of the manifestations of MFS. This is the first case of MFS accompanied with intracardiac solid masses.