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Abstract Background & aim: Malignant pleural effusion is a common complication. Fiberoptic bronchoscopy is a procedure that allows direct visualization and provides biopsy of the injury. The purpose of the current study was to determine the efficiency of Fiberoptic bronchoscopy in the diagnosis of pleural malignancy. Methods: In the present study, fifty-two patients with exudative pleural effusion with unknown origin due to hemoptysis, atelectasis or wide effusion without large displacements mediastinum, and Endobronchial lesions were studied. Patients were investigated under local anesthesia, using fiberoptic bronchoscopes and the findings were recorded. Moreover, washing, microbial sampling and biopsies were conducted. The gathered data were analyzed by the Chi-square test. Results: Using Fiberoptic bronchoscopy in 22 patients (42.3%) led to the diagnosis of the underlying cause of pleural effusion. In cases of blood sputum, the possibility of which fiberoptic bronchoscopy could reveal the cause of pleural effusion was significantly high (p=0.04), but fiberoptic bronchoscopy did not play a major role in the diagnosis of both large effusion and atelectasis. Conclusion: If fiberoptic bronchoscopy is conducted on patients with hemoptysis to evaluate malignant pleural effusion, it can help establish a diagnosis, but is not recommended routinely for these patients. Key words: Fiberoptic Bronchoscopy, Pleural Effusion, Exudate