Lung cancer, breast cancer and lymphoma are the common oncologic causes of malignant pleural effusion, comprising more than the half of the causes. However, an endocrinologic carcinoma associated malignant effusion is very rare. Recently, we encountered a case of papillary thyroid carcinoma causing malignant effusion. An 83-year-old female patient presented with dyspnea due to massive pleural effusion in her left side. The pleural biopsy, pleural fluid cytology and breast needle aspiration biopsy results were consistent with a metastatic papillary thyroid carcinoma. Thyroid ultrasonography showed two thyroid masses, but the patient refused a thyroid biopsy. This case highlights the need for considering the possibility of papillary thyroid carcinoma when the cause of malignant pleural effusion cannot be found because one of the rare clinical manifestations of a papillary thyroid carcinoma can be dyspnea due to malignant effusion.