We report a case of pulmonary oxalosis secondary to invasive Aspergillus niger infection in a 75-year-old patient with chronic obstructive pulmonary disease. Bronchoscopic image revealed predominantly necrotic cellular debris, scattered fungal hyphae, and numerous birefringent calcium oxalate crystals. Bronchoalveolar lavage results were subsequently positive for A. niger infection. Necrotizing pulmonary infection due to A. niger is uncommon. Many Aspergillus species produce oxalic acid as a result of in vivo fermentation. Calcium oxalate crystals are responsible for tissue destruction. The detection of calcium oxalate crystals is strongly suggestive of A. niger infection. This case illustrates that the presence of oxalate crystals in tissue specimens can help diagnose A. niger infection.