Castleman's disease is an unusual disorder characterized by the abnormal proliferation of B lymphocytes and plasma cells in the lymphoid organs. It is subdivided into three histologic variants: hyaline-vascular, plasma cell, and mixed. Most patients are asymptomatic and found incidentally. Pleural effusion is an uncommon manifestation of Castleman's disease. We report a 23-year-old female with localized Castleman's disease associated with massive pleural effusion. This patient is surviving well and has experienced no recurrence since undergoing a surgical resection of the giant lymph node mass.