A 65-year-old woman was urgently admitted to our hospital for antibiotic-resistant fever, hypoxemia, and hyperleukocytosis and was diagnosed with acute monoblastic leukemia. Chest computed tomography revealed interlobular septal thickening, central ground-glass opacity, and a nodular shadow in the left lower lobe. Although several treatments for infectious disease and acute heart failure were administered, they were less effective. Transbronchial lung biopsy was performed on day 7 of hospitalization, and subsequently, pulmonary leukemic infiltration was confirmed. Based on the diagnosis, we decided to start intensive chemotherapy. Consequently, the abnormal lung shadow on computed tomography vanished, and complete hematological remission was achieved. Although acute myeloid leukemia is frequently associated with lung infiltration during onset, it is often difficult to distinguish it from other pulmonary complications. In clinical practice, intensive chemotherapy is often initiated based on the clinical evaluation without pathological confirmation of the lung disease. Our patient was accurately diagnosed based on the pulmonary leukemic infiltration observed pathologically and recovered well. Here we report our case along with a discussion of the relevant literature.