Plastic bronchitis can cause fatal airway obstruction. An 85-year-old woman with no medical history presented to the emergency department of our hospital with progressing respiratory failure and hemoptysis. Bronchoscopy revealed a fibrin-type cast thrombus in the trachea, and plastic bronchitis was diagnosed. Initial treatment involved airway thrombus removal, and the patient survived. However, bleeding persisted for 6 days, and respiratory status showed slight improvement despite ventilatory management. Steroids were administered for concomitant acute respiratory distress syndrome, and there was marked improvement in both airway hemorrhage and respiratory failure. The patient was extubated, the steroid dose was reduced, and no rebleeding was observed. The patient was discharged from the hospital 1 month after the onset of symptoms. Blood tests were positive for the myeloperoxidase-anti-neutrophil cytoplasmic antibody; however, no biopsy was performed, and no specific symptoms were observed. A definitive diagnosis was therefore not reached. The causes of plastic bronchitis are numerous, and there are no standardized diagnostic criteria or treatment guidelines for this condition. The present case suggests that steroids may be effective in some patients with plastic bronchitis.