We report a case of cardiac myxoma with mediastinal lymphadenopathy which seems to be a very rare feature. Laboratory examination revealed high level of interleukin-6 (IL-6) activity in serum. Interestingly, after removal of cardiac myxoma, mediastinal lymphadenopathy disappeared on the chest CT and the level of serum IL-6 was decreased. These findings suggest that IL-6 which was probably derived from myxoma, may have played an important role in the development of lymphadenopathy.