Malignant pleural effusions are common in patients with cancer. Most malignant pleural effusions are secondary to metastases to the pleura, most often from lung or breast cancer. The presence of malignant effusion indicates advanced disease and poor survival; in lung cancer, the presence of malignant effusion upstages the cancer to stage 4. Usually presenting as a large, unilateral exudative effusion, most patients with malignant pleural effusion experience dyspnea. Prior to intervention, diagnosis of malignant pleural effusion and exclusion of infection should be made. Thoracic imaging is typically performed, with computed tomography considered by many to be the gold standard. Thoracic ultrasound is also useful, particularly if diaphragmatic or pleural thickening and nodularity can be identified. Cytology should then be obtained; this is typically done via pleural fluid aspiration or pleural biopsy. Treatment focuses on palliation and relief of symptoms. Numerous interventions are available, ranging from drainage with thoracentesis or indwelling pleural catheter to more definitive, invasive options such as pleurodesis. There is no clear best approach, and a patient-centered approach should be taken.