Bacillus Calmette-Guérin (BCG) is an attenuated strain of Mycobacterium bovis that has been effectively used in the treatment of non-muscle invasive bladder carcinoma. The complications of this treatment are uncommon, and the causes of dissemination are still discussed. We report a case of disseminated tuberculosis in a 66-year-old smoking man without a history of pulmonary diseases, who underwent immunotherapy with BCG after the initial surgical treatment of bladder cancer. After the last BCG instillation, he developed a fever. The diagnosis of sepsis was not confirmed, and miliary pulmonary tuberculosis was suspected. The diagnosis was confirmed by clinical manifestation, computed tomography of the lungs, and histological examination.