We describe the case of a 72-year old male with pleural effusion associated with prostate cancer. There was a previous history of tobacco smoking (pack/year: 47) and of total prostatectomy followed by external beam radiation therapy seven years previously for prostate cancer. Furthermore, he was submitted to orchiectomy plus non-steroidal anti-androgen blockage, in addition to docetaxel-based chemotherapy and prednisone. After the beginning of chemotherapy, a progressive elevation in prostate specific antigen (PSA) levels was observed. On admission, he presented with fever, weight loss, and respiratory symptoms due to a massive right pleural effusion. Fluid samples obtained by needle aspiration showed haemorrhagic exudates without malignant cells. Pleural metastasis were detected by thorax imaging studies, and biopsy samples revealed prostate adenocarcinoma as the origin of his pleural effusion. Pleural fluid was drained and talc pleurodesis was performed. This report aims to describe the occurrence of massive pleural effusion due to metastasis of prostate cancer, and emphasizes the role of pleural biopsy with immunohistochemical studies to characterize this diagnosis.