Pulmonary blastoma (PB) is a rare malignant pulmonary tumor composed of immature mesenchyme and/or epithelium that resembles an embryonic lung at 10-16 weeks gestation. PBs constitute only 0.25 to 0.5 percent of all primary malignant lung tumors. Approximately 20 percent of the reported cases have occurred in pediatric patients. A seven-year-old girl presented with fever, cough, respiratory distress and chest pain on the left side. An x-ray, ultrasonography and a computed tomographic scan of the chest showed a large mass consisting of solid and cystic components almost completely occupying the left hemithorax associated with pleural effusion. The diagnosis of biphasic PB was established by histological examination of thoracotomy material. The patient was considered inoperable due to tumor involvement of the mediastinum, and she died two days after the initiation of chemotherapy. We report this case of PB to raise attention to the clinical, radiological and pathological features of PB in childhood because of its rarity.