BACKGROUND Bronchopulmonary dysplasia (BDP) is an incurable disease. This study reports the successful treatment of a 30-week-old neonate with established bronchopulmonary dysplasia by bone marrow mononuclear cells (BM MNCs) transplantation. CASE REPORT The preterm infant with BPD requiring continuous oxygen administration for 4 months post-delivery underwent BM MNCs. Bone marrow was obtained from the patient's iliac crests and mononuclear cells were isolated by density gradient centrifugation method. BM MNCs were delivered via endotracheal and intravenous routes. After BM MNCs transplantation, remarkable improvements were observed in oxygen saturation and lung CT as the infant was gradually weaned off oxygen supply. CONCLUSIONS BM MNCs transplantation offers promising treatment of BPD.