Thymic basaloid carcinoma is an extremely rare tumor type, with only 10 such reports published to date in the English literature. We herein present a new case of thymic basaloid carcinoma with pleural dissemination that developed after a curative resection. A cystic tumor in the anterior mediastinum was observed in a 72-year-old man, and the tumor was completely resected via a median sternotomy with a combined resection of the adjacent structures. One year later, pleural disseminated nodules developed in the right thorax, which were resected through a right thoracotomy. The present case and the review of previous cases indicated that this rare tumor, which had previously been considered to be a low-grade malignant thymic carcinoma, may therefore have a more obstinate and aggressive malignant nature. Histopathologically, a few CD5-positive tumor cells were observed in isolation in the squamous epithelium of the inner cyst wall, thus suggesting that malignant transformation subsequently occurs in a preexisting cyst.