Abstract. Malignant pleural effusion (MPE) appears in up to 20% of patients with non-Hodgkin's lymphoma (NHL). The present study aimed to assess the efficacy of medical thoracoscopy (MT) in the diagnosis of patients with MPE induced by NHL. Between July 2005 and June 2014, 833 patients with pleural effusions of unknown etiology underwent MT in Beijing Chaoyang Hospital (Beijing, China), where diagnostic thoracocentesis or/and blind pleural biopsy had failed to yield an answer. Demographic, radiographic, thoracoscopic, histological and immunophenotyping data of 10 NHL patients with MPE were then retrospectively analyzed. Under medical thoracoscopy, pleural nodules (in n=6 patients), hyperemia (n=5), plaque-like lesions (n=4), pleural thickening (n=3), cellulose (n=3), ulcer (n=2), adhesion (n=2), and scattered hemorrhagic spots (n=1) were observed on the surface of parietal pleura. Histopathological and immunohistochemical analysis of pleural biopsy samples led to a correct diagnosis of B-cell NHL in 7 patients and T-lymphoblastic NHL in 2 patients.Data from the present study demonstrated that pleural biopsy through MT achieved a definite diagnosis of NHL in 9 out of 10 (90%) patients with MPE induced by NHL. Therefore, MT is a useful method for diagnosing MPE induced by NHL.