Cytomegalovirus pneumonitis in a patient with pulmonary tuberculosis has been rarely reported. We report on a patient with nephrotic syndrome and documented pulmonary tuberculosis who received antituberculous therapy. Chest radiography showed a newly developed patch, and he underwent high-resolution computed tomography examination of the chest and open lung biopsy. Histopathologic studies of the lung showed interstitial pneumonitis, which had focal syncytial pneumocytes with focal nuclei atypia, inclusion bodies, and prominent eosinophilic nucleoli. Polymerase chain reactions for cytomegalovirus were positive in the sputum and biopsy specimen. The patient recovered well with ganciclovir treatment. When new pulmonary infiltrates develop in patients with pulmonary tuberculosis during antituberculous therapy, cytomegalovirus pneumonitis should not be overlooked.