Nontraumatic chylous pleural effusions (chylothorax) and pericardial effusions (chylopericardium) are rare. They can, however, accompany intrathoracic malignancies and, most commonly, lymphomas. An association of chronic lymphocytic leukemia (cll) with chylopericardium has rarely been reported. A 68-year-old woman with cll, previously treated with single-agent fludarabine in the community, developed pleuritic chest pain and a new pericardial effusion. Computed tomography (ct) imaging of her chest revealed a large pericardial effusion with progressive lymphadenopathy. Pericardiocentesis identified a chylous effusion, and complete evacuation was achieved by catheter drainage. The cll was not treated. An asymptomatic pericardial effusion subsequently recurred. Pericardiocentesis was not repeated. Lymph node biopsy and flow cytometry revealed no evidence of large-cell lymphoma transformation. The patient was treated with 6 cycles of chlorambucil and obinutuzumab. Imaging of her chest by ct between cycles 2 and 3 revealed a marked resolution of the intrathoracic lymphadenopathy, with complete disappearance of the pericardial effusion. Repeat imaging at 5 months and again at 3 years after completion of chemotherapy demonstrated no recurrence of either the lymphadenopathy or the pericardial effusion. The mechanism of production and the treatment of chylous effusions are poorly defined. In this case, resolution of the pericardial effusion with effective chemotherapy is postulated to have alleviated obstruction of anterograde lymphatic flow facilitating drainage into the systemic venous system and allowing for spontaneous complete resolution of the pericardial effusion without surgical intervention.