In clinical practice, we encounter pleural effusion in pleurisy, and more than 80-90% of cases are resolved with appropriate treatment[5]. Despite the initial diagnosis, a significant part of pleural effusions remains undiagnosed[1]. Pleural fluid cytology has a low sensitivity of 58.2% for malignancy, which does not differ by tumor type even with repeated testing[1]. Pleural biopsy via thoracoscopy has a much higher diagnostic yield for malignancy, especially mesothelioma, with a low complication rate[1]. The combination of thoracoscopic visual assessment, touch preparations and pleural nodules on CT has a 94% predictive accuracy for malignant effusion[1]. In countries endemic for tuberculosis, the yield of closed needle biopsy of the pleura is high, while adenosine deaminase in pleural fluid has a sensitivity of 87.5% and a specificity of 87.82%[1]. Management of undiagnosed pleural effusion requires a thorough and systematic approach focused on patient outcomes[1].