A 42-year-old man presented to our hospital for hilar lymphadenopathy and a nodule in the left lower lung field with no symptoms. The nodule had been noted in a medical exam performed 1 year earlier, just after the patient had returned to Japan from the United States. Chest computed tomography showed a left-sided pulmonary nodule and hilar and mediastinal lymphadenopathy. A lung specimen obtained via thoracoscopy showed yeastlike fungi, and serum antibody against Histoplasma capsulatum was positive. The results of polymerase chain reaction analysis of the resected pulmonary specimen were compatible with H. capsulatum. Mediastinal lesion was regarded as a mediastinal granuloma on the basis of the clinical course and radiological findings. Fluconazole was administered, which shrunk the mediastinal lesion. We report this case because in Japan there have been no previous reports of pulmonary histoplasmosis developing a mediastinal granuloma.