Although papillary carcinoma of the thyroid generally follows an indolent course characterized by slow growth and the absence of distant metastases, several available reports suggest that metastasis to bone and/or lung parenchyma may occur infrequently. But pleural metastases are known to be very rare, so there have been only two case reports about the pleural metastases of papillary thyroid carcinoma in the literatures. Even the case of occult papillary thyroid carcinoma presenting as a metastatic pleural effusion has been never been reported. Recently we experienced a case with the chief complaint of dyspnea due to massive pleural effusion, the cytologic examination of which revealed the papillary carcinoma with psamomma bodies. The examination of the thyroid revealed no definite primary tumor. The total thyroidectomy was done with the plan of post-operative radioactive iodine treatment and the pathologic result confirmed the occult papillary microcarcinoma as expected. With the present case report, the extension of the clinical spectrum. of metastatic papillary carcinoma of the thyroid is expected.