A lymphocele is defined as a circumscribed collection of protein-rich lymphatic fluid without an epithelial lining that develops in anatomic compartments as the result of trauma or interruption to the lymphatic system. Because lymphatic fluid is protein rich and devoid of platelets or clotting factors, a transected lymphatic channel cannot clot and is therefore prone to leakage, resulting in a lymphocele. Although lymphocele formation is a well-known complication of surgery in and around the inguinal and femoral vessels, they are not commonly described in the mediastinum. Mediastinal lymphoceles form as a rare consequence of lymphatic damage during cardiothoracic surgery or blunt chest trauma. They may appear days to years after the injury. Most lymphoceles, also referred to as chylous pseudocysts, cystic lymphangiomas, and lymphatic duct hygromas, are small, sterile, and asymptomatic, and they resolve spontaneously by reabsorption. However, a few may enlarge and cause symptoms related to compression, such as dysphagia, dyspnea, and chest pain, or signs of infection.