Pulmonary complications occur in up to 60% of patients after hematopoietic stem cell transplantation (HSCT), causing significant morbidity and mortality. Among them, non-infectious bronchiolitis is considered a late complication in the form of bronchiolitis obliterans. We report a patient who developed non-infectious bronchiolitis within four weeks after undergoing HSCT for biphenotypic leukemia. Chest CT revealed centrilobular nodules that were reminiscent of diffuse panbronchiolitis, and lymphocytic bronchiolitis was confirmed by biopsy. Infection and bronchiolitis obliterans were ruled out, and the bronchiolitis resolved when leukemia relapsed. This case suggests that bronchiolitis may be another early, non-infectious pulmonary complication of HSCT.