Bilateral chylothorax is a rare complication of neck dissection, but it is potentially serious and sometimes life threatening. Because of the rarity of chylothorax, surgeons are unfamiliar with its early signs, which allow a prompt diagnosis and effective management. Most cases reported in the literature were associated with a concurrent external chyle leakage, which occurred either during or after surgery. We report two cases of bilateral chylothoraces without concurrent external chyle leakage, which occurred after left-sided neck dissections for thyroid cancer. We treated both patients successfully with conservative management.