Aspergillus udagawae and A. fumigatus share similar morphological features but they differ genetically. There is also an important clinical distinction as A. udagawae is less sensitive to amphotericin B than A. fumigatus. We encountered a rare case of bronchial infection due to A. udagawae that was successfully treated with voriconazole. An 82-year-old woman with diabetes mellitus complained of bloody sputum. Bronchoscopy revealed a white plugged region at the origin of the right bronchi B5. Cytological study revealed a clot composed of filamentous fungi and Aspergillus spp. was detected by culture. Molecular analysis revealed that the causative agent was A. udagawae, and voriconazole was used for the treatment. In comparison to A. fumigatus, the A. udagawae strain isolated in this case was less sensitive to amphotericin B, less virulent in immunosuppressed mice, and more sensitive to hydrogen peroxide, features that are almost identical to those of the previously reported isolates of the fungus. We should be aware of the emergence of new Aspergillus species that might pose a clinical threat.