We report the case of a Peruvian man in his 50s who immigrated to Japan in March 20XX. He developed prolonged fever in April, for which he visited a doctor in June. He was referred to our hospital because he tested positive for human immunodeficiency virus, and chest computed tomography revealed bilateral diffuse micronodules. His cluster of differentiation 4⁺ count was low at 54/μL, and he developed acquired immunodeficiency syndrome at that point. Initially, miliary tuberculosis was suspected; however, the patient tested negative for T-SPOT.TB, and mycobacteria could not be detected in a series of culture tests. We performed bronchoscopy and found yeast-like fungi in the transbronchial lung biopsy specimen, suggesting disseminated mycosis. The test result for serum cryptococcal antigen was negative, and histoplasmosis was suspected owing to the patient's Peruvian origin. The result of the urinary antigen test for Histoplasma capsulatum was positive approximately 2 weeks later, thereby confirming a definitive diagnosis of disseminated histoplasmosis. We initiated intravenous liposomal amphotericin B (L-AMB) therapy for 1 month before switching to maintenance therapy with oral itraconazole (ITCZ). The treatments were successful; the micronodules and symptoms resolved. In Japan, histoplasmosis is an unfamiliar disease; however, in endemic areas, including the Americas, it is common. Herein, we report an imported case to raise awareness among Japanese clinicians.