Sarcoidosis is a somewhat common pulmonary disease, but the concurrence of lung cancer and sarcoidosis in the same patient is very rare. Because sarcoidosis usually presents as mediastinal lymphadenopathies, this concurrence in a lung cancer patient detected radiologically is apt to be misunderstood to be mediastinal metastases, and it is thus considered to be an unresectable disease. We report a case of lung cancer associated with sarcoidosis that developed in a 65-year-old woman who underwent surgery. Radiological studies revealed a 1.9×1.7 cm mass in the left upper lobe with multiple enlarged bilateral mediastinal lymph nodes (2R, 3a, 4R, 4L, 5, 6, 7, 8R). Pathologic findings showed that the mass was a well-differentiated adenocarcinoma and all of the enlarged mediastinal lymph nodes were granulomas without cancer metastasis. We report this case with a review of the literature.