A 65-year-old diabetic female patient presented with dyspnea and respiratory distress before admission. Hyperglycemia was evident on admission, and diabetic ketoacidosis (DKA) was confirmed. She was intubated with ventilator support due to respiratory failure. The clinical course improved despite progressive pulmonary infiltration and cavitation after extubation. Pulmonary aspergillosis was confirmed by bronchial biopsy. Chronic necrotizing pulmonary aspergillosis (CNPA) was highly likely, based on the patient's subacute course. But the diagnosis was delayed, which could have led to more morbidity and a greater chance of mortality. Despite a two-month delay in diagnosis for this patient, her lung lesion completely regressed after a nearly 6-month outpatient antifungal therapy regimen with itraconazole.